diff --git a/src/renderers/dom/client/ReactMount.js b/src/renderers/dom/client/ReactMount.js
index 57af82b39e..88ed3a01a8 100644
--- a/src/renderers/dom/client/ReactMount.js
+++ b/src/renderers/dom/client/ReactMount.js
@@ -28,7 +28,6 @@ var ReactUpdateQueue = require('ReactUpdateQueue');
 var ReactUpdates = require('ReactUpdates');
 
 var emptyObject = require('emptyObject');
-var containsNode = require('containsNode');
 var instantiateReactComponent = require('instantiateReactComponent');
 var invariant = require('invariant');
 var setInnerHTML = require('setInnerHTML');
@@ -36,7 +35,6 @@ var shouldUpdateReactComponent = require('shouldUpdateReactComponent');
 var warning = require('warning');
 
 var ATTR_NAME = DOMProperty.ID_ATTRIBUTE_NAME;
-var nodeCache = {};
 
 var ELEMENT_NODE_TYPE = 1;
 var DOC_NODE_TYPE = 9;
@@ -54,9 +52,6 @@ if (__DEV__) {
   var rootElementsByReactRootID = {};
 }
 
-// Used to store breadth-first search state in findComponentRoot.
-var findComponentRootReusableArray = [];
-
 /**
  * Finds the index of the first character
  * that's not common between the two given strings.
@@ -99,33 +94,6 @@ function getReactRootID(container) {
   return rootElement && internalGetID(rootElement);
 }
 
-/**
- * Accessing node[ATTR_NAME] or calling getAttribute(ATTR_NAME) on a form
- * element can return its control whose name or ID equals ATTR_NAME. All
- * DOM nodes support `getAttributeNode` but this can also get called on
- * other objects so just return '' if we're given something other than a
- * DOM node (such as window).
- *
- * @param {?DOMElement|DOMWindow|DOMDocument|DOMTextNode} node DOM node.
- * @return {string} ID of the supplied `domNode`.
- */
-function getID(node) {
-  var id = internalGetID(node);
-  if (id) {
-    var cached = nodeCache[id];
-    // TODO: Fix this whole concept of "validity" -- the cache just shouldn't
-    // have nodes that have been unmounted.
-    invariant(
-      !cached || cached === node || !isValid(cached, id),
-      'ReactMount: Two valid but unequal nodes with the same `%s`: %s',
-      ATTR_NAME, id
-    );
-    nodeCache[id] = node;
-  }
-
-  return id;
-}
-
 function internalGetID(node) {
   // If node is something like a window, document, or text node, none of
   // which support attributes or a .getAttribute method, gracefully return
@@ -133,112 +101,6 @@ function internalGetID(node) {
   return node && node.getAttribute && node.getAttribute(ATTR_NAME) || '';
 }
 
-/**
- * Sets the React-specific ID of the given node.
- *
- * @param {DOMElement} node The DOM node whose ID will be set.
- * @param {string} id The value of the ID attribute.
- */
-function setID(node, id) {
-  var oldID = internalGetID(node);
-  if (oldID !== id) {
-    delete nodeCache[oldID];
-  }
-  node.setAttribute(ATTR_NAME, id);
-  nodeCache[id] = node;
-}
-
-/**
- * Finds the node with the supplied ID if present in the cache.
- */
-function getNodeIfCached(id) {
-  var node = nodeCache[id];
-  // TODO: Fix this whole concept of "validity" -- the cache just shouldn't have
-  // nodes that have been unmounted.
-  if (node && isValid(node, id)) {
-    return node;
-  }
-}
-
-/**
- * Finds the node with the supplied React-generated DOM ID.
- *
- * @param {string} id A React-generated DOM ID.
- * @return {DOMElement} DOM node with the suppled `id`.
- * @internal
- */
-function getNode(id) {
-  var node = getNodeIfCached(id);
-  if (node) {
-    return node;
-  } else {
-    return nodeCache[id] = ReactMount.findReactNodeByID(id);
-  }
-}
-
-/**
- * A node is "valid" if it is contained by a currently mounted container.
- *
- * This means that the node does not have to be contained by a document in
- * order to be considered valid.
- *
- * @param {?DOMElement} node The candidate DOM node.
- * @param {string} id The expected ID of the node.
- * @return {boolean} Whether the node is contained by a mounted container.
- */
-function isValid(node, id) {
-  if (node) {
-    invariant(
-      internalGetID(node) === id,
-      'ReactMount: Unexpected modification of `%s`',
-      ATTR_NAME
-    );
-
-    var container = ReactMount.findReactContainerForID(id);
-    if (container && containsNode(container, node)) {
-      return true;
-    }
-  }
-
-  return false;
-}
-
-/**
- * Causes the cache to forget about one React-specific ID.
- *
- * @param {string} id The ID to forget.
- */
-function purgeID(id) {
-  delete nodeCache[id];
-}
-
-var deepestNodeSoFar = null;
-function findDeepestCachedAncestorImpl(ancestorID) {
-  var ancestor = getNodeIfCached(ancestorID);
-  if (ancestor) {
-    deepestNodeSoFar = ancestor;
-  } else {
-    // This node isn't populated in the cache, so presumably none of its
-    // descendants are. Break out of the loop.
-    return false;
-  }
-}
-
-/**
- * Return the deepest cached node whose ID is a prefix of `targetID`.
- */
-function findDeepestCachedAncestor(targetID) {
-  deepestNodeSoFar = null;
-  ReactInstanceHandles.traverseAncestors(
-    targetID,
-    findDeepestCachedAncestorImpl
-  );
-
-  var foundNode = deepestNodeSoFar;
-  deepestNodeSoFar = null;
-  return foundNode;
-}
-
 /**
  * Mounts this component and inserts it into the DOM.
  *
@@ -344,47 +206,6 @@ function hasNonRootReactChild(node) {
     ReactInstanceHandles.getReactRootIDFromNodeID(reactRootID) : false;
 }
 
-/**
- * Returns the first (deepest) ancestor of a node which is rendered by this copy
- * of React.
- */
-function findFirstReactDOMImpl(node) {
-  // This node might be from another React instance, so we make sure not to
-  // examine the node cache here
-  for (; node && node.parentNode !== node; node = node.parentNode) {
-    if (node.nodeType !== 1) {
-      // Not a DOMElement, therefore not a React component
-      continue;
-    }
-    var nodeID = internalGetID(node);
-    if (!nodeID) {
-      continue;
-    }
-    var reactRootID = ReactInstanceHandles.getReactRootIDFromNodeID(nodeID);
-
-    // If containersByReactRootID contains the container we find by crawling up
-    // the tree, we know that this instance of React rendered the node.
-    // nb. isValid's strategy (with containsNode) does not work because render
-    // trees may be nested and we don't want a false positive in that case.
-    var current = node;
-    var lastID;
-    do {
-      lastID = internalGetID(current);
-      current = current.parentNode;
-      if (current == null) {
-        // The passed-in node has been detached from the container it was
-        // originally rendered into.
-        return null;
-      }
-    } while (lastID !== reactRootID);
-
-    if (current === containersByReactRootID[reactRootID]) {
-      return node;
-    }
-  }
-  return null;
-}
-
 /**
  * Temporary (?) hack so that we can store all top-level pending updates on
  * composites instead of having to worry about different types of components
@@ -794,162 +615,6 @@ var ReactMount = {
     return true;
   },
 
-  /**
-   * Finds the container DOM element that contains React component to which the
-   * supplied DOM `id` belongs.
-   *
-   * @param {string} id The ID of an element rendered by a React component.
-   * @return {?DOMElement} DOM element that contains the `id`.
-   */
-  findReactContainerForID: function(id) {
-    var reactRootID = ReactInstanceHandles.getReactRootIDFromNodeID(id);
-    var container = containersByReactRootID[reactRootID];
-
-    if (__DEV__) {
-      var rootElement = rootElementsByReactRootID[reactRootID];
-      if (rootElement && rootElement.parentNode !== container) {
-        warning(
-          // Call internalGetID here because getID calls isValid which calls
-          // findReactContainerForID (this function).
-          internalGetID(rootElement) === reactRootID,
-          'ReactMount: Root element ID differed from reactRootID.'
-        );
-        var containerChild = container.firstChild;
-        if (containerChild &&
-            reactRootID === internalGetID(containerChild)) {
-          // If the container has a new child with the same ID as the old
-          // root element, then rootElementsByReactRootID[reactRootID] is
-          // just stale and needs to be updated. The case that deserves a
-          // warning is when the container is empty.
-          rootElementsByReactRootID[reactRootID] = containerChild;
-        } else {
-          warning(
-            false,
-            'ReactMount: Root element has been removed from its original ' +
-            'container. New container: %s',
-            rootElement.parentNode
-          );
-        }
-      }
-    }
-
-    return container;
-  },
-
-  /**
-   * Finds an element rendered by React with the supplied ID.
-   *
-   * @param {string} id ID of a DOM node in the React component.
-   * @return {DOMElement} Root DOM node of the React component.
-   */
-  findReactNodeByID: function(id) {
-    var reactRoot = ReactMount.findReactContainerForID(id);
-    return ReactMount.findComponentRoot(reactRoot, id);
-  },
-
-  /**
-   * Traverses up the ancestors of the supplied node to find a node that is a
-   * DOM representation of a React component rendered by this copy of React.
-   *
-   * @param {*} node
-   * @return {?DOMEventTarget}
-   * @internal
-   */
-  getFirstReactDOM: function(node) {
-    return findFirstReactDOMImpl(node);
-  },
-
-  /**
-   * Finds a node with the supplied `targetID` inside of the supplied
-   * `ancestorNode`.  Exploits the ID naming scheme to perform the search
-   * quickly.
-   *
-   * @param {DOMEventTarget} ancestorNode Search from this root.
-   * @pararm {string} targetID ID of the DOM representation of the component.
-   * @return {DOMEventTarget} DOM node with the supplied `targetID`.
-   * @internal
-   */
-  findComponentRoot: function(ancestorNode, targetID) {
-    var firstChildren = findComponentRootReusableArray;
-    var childIndex = 0;
-
-    var deepestAncestor = findDeepestCachedAncestor(targetID) || ancestorNode;
-
-    if (__DEV__) {
-      // This will throw on the next line; give an early warning
-      warning(
-        deepestAncestor != null,
-        'React can\'t find the root component node for data-reactid value ' +
-        '`%s`. If you\'re seeing this message, it probably means that ' +
-        'you\'ve loaded two copies of React on the page. At this time, only ' +
-        'a single copy of React can be loaded at a time.',
-        targetID
-      );
-    }
-
-    firstChildren[0] = deepestAncestor.firstChild;
-    firstChildren.length = 1;
-
-    while (childIndex < firstChildren.length) {
-      var child = firstChildren[childIndex++];
-      var targetChild;
-
-      while (child) {
-        var childID = ReactMount.getID(child);
-        if (childID) {
-          // Even if we find the node we're looking for, we finish looping
-          // through its siblings to ensure they're cached so that we don't have
-          // to revisit this node again. Otherwise, we make n^2 calls to getID
-          // when visiting the many children of a single node in order.
-
-          if (targetID === childID) {
-            targetChild = child;
-          } else if (ReactInstanceHandles.isAncestorIDOf(childID, targetID)) {
-            // If we find a child whose ID is an ancestor of the given ID,
-            // then we can be sure that we only want to search the subtree
-            // rooted at this child, so we can throw out the rest of the
-            // search state.
-            firstChildren.length = childIndex = 0;
-            firstChildren.push(child.firstChild);
-          }
-
-        } else {
-          // If this child had no ID, then there's a chance that it was
-          // injected automatically by the browser, as when a `<table>`
-          // element sprouts an extra `<tbody>` child as a side effect of
-          // `.innerHTML` parsing. Optimistically continue down this
-          // branch, but not before examining the other siblings.
-          firstChildren.push(child.firstChild);
-        }
-
-        child = child.nextSibling;
-      }
-
-      if (targetChild) {
-        // Emptying firstChildren/findComponentRootReusableArray is
-        // not necessary for correctness, but it helps the GC reclaim
-        // any nodes that were left at the end of the search.
-        firstChildren.length = 0;
-
-        return targetChild;
-      }
-    }
-
-    firstChildren.length = 0;
-
-    invariant(
-      false,
-      'findComponentRoot(..., %s): Unable to find element. This probably ' +
-      'means the DOM was unexpectedly mutated (e.g., by the browser), ' +
-      'usually due to forgetting a <tbody> when using tables, nesting tags ' +
-      'like <form>, <p>, or <a>, or using non-SVG elements in an <svg> ' +
-      'parent. ' +
-      'Try inspecting the child nodes of the element with React ID `%s`.',
-      targetID,
-      ReactMount.getID(ancestorNode)
-    );
-  },
-
   _mountImageIntoNode: function(
     markup,
     container,
@@ -1056,22 +721,6 @@ var ReactMount = {
       ReactDOMComponentTree.precacheNode(instance, container.firstChild);
     }
   },
-
-  /**
-   * React ID utilities.
-   */
-
-  getReactRootID: getReactRootID,
-
-  getID: getID,
-
-  setID: setID,
-
-  getNode: getNode,
-
-  isValid: isValid,
-
-  purgeID: purgeID,
 };
 
 ReactPerf.measureMethods(ReactMount, 'ReactMount', {
diff --git a/src/renderers/dom/client/__tests__/ReactMount-test.js b/src/renderers/dom/client/__tests__/ReactMount-test.js
index 4e5915c034..bbeb67620b 100644
--- a/src/renderers/dom/client/__tests__/ReactMount-test.js
+++ b/src/renderers/dom/client/__tests__/ReactMount-test.js
@@ -218,61 +218,6 @@ describe('ReactMount', function() {
     );
   });
 
-  it('should not crash in node cache when unmounting', function() {
-    var Component = React.createClass({
-      render: function() {
-        // Add refs to some nodes so that they get traversed and cached
-        return (
-          <div ref="a">
-            <div ref="b">b</div>
-            {this.props.showC && <div>c</div>}
-          </div>
-        );
-      },
-    });
-
-    var container = document.createElement('container');
-
-    ReactDOM.render(<div><Component showC={false} /></div>, container);
-
-    // Right now, A and B are in the cache. When we add C, it won't get added to
-    // the cache (assuming markup-string mode).
-    ReactDOM.render(<div><Component showC={true} /></div>, container);
-
-    // Remove A, B, and C. Unmounting C shouldn't cause B to get recached.
-    ReactDOM.render(<div></div>, container);
-
-    // Add them back -- this shouldn't cause a cached node collision.
-    ReactDOM.render(<div><Component showC={true} /></div>, container);
-
-    ReactDOM.unmountComponentAtNode(container);
-  });
-
-  it('should not crash in node cache when unmounting, case 2', function() {
-    var A = React.createClass({
-      render: function() {
-        return <a key={this.props.innerKey}>{this.props.innerKey}</a>;
-      },
-    });
-    var Component = React.createClass({
-      render: function() {
-        return (
-          <b>
-            <i>{this.props.step === 1 && <q />}</i>
-            {this.props.step === 1 && <A innerKey={this.props.step} />}
-          </b>
-        );
-      },
-    });
-
-    var container = document.createElement('container');
-
-    ReactDOM.render(<Component step={1} />, container);
-    ReactDOM.render(<Component step={2} />, container);
-    ReactDOM.render(<Component step={1} />, container);
-    ReactMount.getID(container.querySelector('a'));
-  });
-
   it('passes the correct callback context', function() {
     var container = document.createElement('div');
     var calls = 0;
diff --git a/src/renderers/dom/client/__tests__/ReactRenderDocument-test.js b/src/renderers/dom/client/__tests__/ReactRenderDocument-test.js
index 2c9d642724..02230bf46b 100644
--- a/src/renderers/dom/client/__tests__/ReactRenderDocument-test.js
+++ b/src/renderers/dom/client/__tests__/ReactRenderDocument-test.js
@@ -17,8 +17,6 @@ jest
 var React;
 var ReactDOM;
 var ReactDOMServer;
-var ReactInstanceMap;
-var ReactMount;
 
 var getTestDocument;
 
@@ -46,14 +44,12 @@ describe('rendering React components at document', function() {
     React = require('React');
     ReactDOM = require('ReactDOM');
     ReactDOMServer = require('ReactDOMServer');
-    ReactInstanceMap = require('ReactInstanceMap');
-    ReactMount = require('ReactMount');
     getTestDocument = require('getTestDocument');
 
     testDocument = getTestDocument();
   });
 
-  it('should be able to get root component id for document node', function() {
+  it('should be able to adopt server markup', function() {
     expect(testDocument).not.toBeUndefined();
 
     var Root = React.createClass({
@@ -64,22 +60,24 @@ describe('rendering React components at document', function() {
               <title>Hello World</title>
             </head>
             <body>
-              Hello world
+              {'Hello ' + this.props.hello}
             </body>
           </html>
         );
       },
     });
 
-    var markup = ReactDOMServer.renderToString(<Root />);
+    var markup = ReactDOMServer.renderToString(<Root hello="world" />);
     testDocument = getTestDocument(markup);
-    var component = ReactDOM.render(<Root />, testDocument);
+    var body = testDocument.body;
+
+    ReactDOM.render(<Root hello="world" />, testDocument);
     expect(testDocument.body.innerHTML).toBe('Hello world');
 
-    // TODO: This is a bad test. I have no idea what this is testing.
-    // Node IDs is an implementation detail and not part of the public API.
-    var componentID = ReactMount.getReactRootID(testDocument);
-    expect(componentID).toBe(ReactInstanceMap.get(component)._rootNodeID);
+    ReactDOM.render(<Root hello="moon" />, testDocument);
+    expect(testDocument.body.innerHTML).toBe('Hello moon');
+
+    expect(body).toBe(testDocument.body);
   });
 
   it('should not be able to unmount component from document node', function() {
diff --git a/src/renderers/dom/client/wrappers/ReactDOMInput.js b/src/renderers/dom/client/wrappers/ReactDOMInput.js
index 52fce3cdae..682a34961a 100644
--- a/src/renderers/dom/client/wrappers/ReactDOMInput.js
+++ b/src/renderers/dom/client/wrappers/ReactDOMInput.js
@@ -14,7 +14,6 @@
 var DOMPropertyOperations = require('DOMPropertyOperations');
 var LinkedValueUtils = require('LinkedValueUtils');
 var ReactDOMComponentTree = require('ReactDOMComponentTree');
-var ReactMount = require('ReactMount');
 var ReactUpdates = require('ReactUpdates');
 
 var assign = require('Object.assign');
@@ -189,18 +188,12 @@ function _handleChange(event) {
       // This will throw if radio buttons rendered by different copies of React
       // and the same name are rendered into the same form (same as #1939).
       // That's probably okay; we don't support it just as we don't support
-      // mixing React with non-React.
-      var otherID = ReactMount.getID(otherNode);
-      invariant(
-        otherID,
-        'ReactDOMInput: Mixing React and non-React radio inputs with the ' +
-        'same `name` is not supported.'
-      );
-      var otherInstance = instancesByReactID[otherID];
+      // mixing React radio buttons with non-React ones.
+      var otherInstance = ReactDOMComponentTree.getInstanceFromNode(otherNode);
       invariant(
         otherInstance,
-        'ReactDOMInput: Unknown radio button ID %s.',
-        otherID
+        'ReactDOMInput: Mixing React and non-React radio inputs with the ' +
+        'same `name` is not supported.'
       );
       // If this is a controlled radio button group, forcing the input that
       // was previously checked to update will cause it to be come re-checked
diff --git a/src/renderers/dom/shared/ReactComponentBrowserEnvironment.js b/src/renderers/dom/shared/ReactComponentBrowserEnvironment.js
index 3f31a52a21..d10cca3054 100644
--- a/src/renderers/dom/shared/ReactComponentBrowserEnvironment.js
+++ b/src/renderers/dom/shared/ReactComponentBrowserEnvironment.js
@@ -13,7 +13,6 @@
 
 var DOMChildrenOperations = require('DOMChildrenOperations');
 var ReactDOMIDOperations = require('ReactDOMIDOperations');
-var ReactMount = require('ReactMount');
 var ReactPerf = require('ReactPerf');
 
 /**
@@ -37,7 +36,6 @@ var ReactComponentBrowserEnvironment = {
    * @private
    */
   unmountIDFromEnvironment: function(rootNodeID) {
-    ReactMount.purgeID(rootNodeID);
   },
 
 };
diff --git a/src/renderers/dom/shared/ReactDOMComponent.js b/src/renderers/dom/shared/ReactDOMComponent.js
index b6cff58787..d363c242de 100644
--- a/src/renderers/dom/shared/ReactDOMComponent.js
+++ b/src/renderers/dom/shared/ReactDOMComponent.js
@@ -33,7 +33,6 @@ var ReactDOMInput = require('ReactDOMInput');
 var ReactDOMOption = require('ReactDOMOption');
 var ReactDOMSelect = require('ReactDOMSelect');
 var ReactDOMTextarea = require('ReactDOMTextarea');
-var ReactMount = require('ReactMount');
 var ReactMultiChild = require('ReactMultiChild');
 var ReactPerf = require('ReactPerf');
 var ReactUpdateQueue = require('ReactUpdateQueue');
@@ -662,8 +661,6 @@ ReactDOMComponent.Mixin = {
       ReactDOMComponentTree.precacheNode(this, el);
       this._flags |= Flags.hasCachedChildNodes;
       DOMPropertyOperations.setAttributeForID(el, this._rootNodeID);
-      // Populate node cache
-      ReactMount.getID(el);
       this._updateDOMProperties(null, props, transaction);
       var lazyTree = DOMLazyTree(el);
       this._createInitialChildren(transaction, props, context, lazyTree);
diff --git a/src/renderers/dom/shared/ReactDOMTextComponent.js b/src/renderers/dom/shared/ReactDOMTextComponent.js
index 49e9f72291..ff94cbd8e8 100644
--- a/src/renderers/dom/shared/ReactDOMTextComponent.js
+++ b/src/renderers/dom/shared/ReactDOMTextComponent.js
@@ -18,7 +18,6 @@ var DOMPropertyOperations = require('DOMPropertyOperations');
 var ReactComponentBrowserEnvironment =
   require('ReactComponentBrowserEnvironment');
 var ReactDOMComponentTree = require('ReactDOMComponentTree');
-var ReactMount = require('ReactMount');
 
 var assign = require('Object.assign');
 var escapeTextContentForBrowser = require('escapeTextContentForBrowser');
@@ -99,10 +98,8 @@ assign(ReactDOMTextComponent.prototype, {
     if (transaction.useCreateElement) {
       var ownerDocument = nativeContainerInfo._ownerDocument;
       var el = ownerDocument.createElement('span');
-      this._nativeNode = el;
+      ReactDOMComponentTree.precacheNode(this, el);
       DOMPropertyOperations.setAttributeForID(el, rootID);
-      // Populate node cache
-      ReactMount.getID(el);
       var lazyTree = DOMLazyTree(el);
       DOMLazyTree.queueText(lazyTree, this._stringText);
       return lazyTree;
diff --git a/src/renderers/shared/reconciler/__tests__/ReactCompositeComponent-test.js b/src/renderers/shared/reconciler/__tests__/ReactCompositeComponent-test.js
index 298c5a1be2..c5ff51e1df 100644
--- a/src/renderers/shared/reconciler/__tests__/ReactCompositeComponent-test.js
+++ b/src/renderers/shared/reconciler/__tests__/ReactCompositeComponent-test.js
@@ -16,7 +16,6 @@ var MorphingComponent;
 var React;
 var ReactDOM;
 var ReactCurrentOwner;
-var ReactMount;
 var ReactPropTypes;
 var ReactServerRendering;
 var ReactTestUtils;
@@ -34,7 +33,6 @@ describe('ReactCompositeComponent', function() {
     ReactCurrentOwner = require('ReactCurrentOwner');
     ReactPropTypes = require('ReactPropTypes');
     ReactTestUtils = require('ReactTestUtils');
-    ReactMount = require('ReactMount');
     ReactServerRendering = require('ReactServerRendering');
     ReactUpdates = require('ReactUpdates');
 
@@ -487,8 +485,6 @@ describe('ReactCompositeComponent', function() {
     var container = document.createElement('div');
     var innerUnmounted = false;
 
-    spyOn(ReactMount, 'purgeID').andCallThrough();
-
     var Component = React.createClass({
       render: function() {
         return (
@@ -501,11 +497,6 @@ describe('ReactCompositeComponent', function() {
     });
     var Inner = React.createClass({
       componentWillUnmount: function() {
-        // It's important that ReactMount.purgeID is called after any component
-        // lifecycle methods, because a componentWillUnmount implementation is
-        // likely to call ReactDOM.findDOMNode(this), which will repopulate the
-        // node cache after it's been cleared, causing a memory leak.
-        expect(ReactMount.purgeID.calls.length).toBe(0);
         innerUnmounted = true;
       },
       render: function() {
@@ -516,12 +507,6 @@ describe('ReactCompositeComponent', function() {
     ReactDOM.render(<Component />, container);
     ReactDOM.unmountComponentAtNode(container);
     expect(innerUnmounted).toBe(true);
-
-    // The text and both <div /> elements and their wrappers each call
-    // unmountIDFromEnvironment which calls purgeID, for a total of 3.
-    // TODO: Test the effect of this. E.g. does the node cache get repopulated
-    // after a getDOMNode call?
-    expect(ReactMount.purgeID.calls.length).toBe(3);
   });
 
   it('should warn when shouldComponentUpdate() returns undefined', function() {
diff --git a/src/renderers/shared/reconciler/__tests__/ReactIdentity-test.js b/src/renderers/shared/reconciler/__tests__/ReactIdentity-test.js
index f0b6b5bd9f..2639ffb2d3 100644
--- a/src/renderers/shared/reconciler/__tests__/ReactIdentity-test.js
+++ b/src/renderers/shared/reconciler/__tests__/ReactIdentity-test.js
@@ -13,9 +13,9 @@
 
 var React;
 var ReactDOM;
+var ReactDOMComponentTree;
 var ReactFragment;
 var ReactTestUtils;
-var ReactMount;
 
 describe('ReactIdentity', function() {
 
@@ -23,14 +23,16 @@ describe('ReactIdentity', function() {
     jest.resetModuleRegistry();
     React = require('React');
     ReactDOM = require('ReactDOM');
+    ReactDOMComponentTree = require('ReactDOMComponentTree');
     ReactFragment = require('ReactFragment');
     ReactTestUtils = require('ReactTestUtils');
-    ReactMount = require('ReactMount');
   });
 
   var idExp = /^\.[^.]+(.*)$/;
   function checkID(child, expectedID) {
-    var actual = idExp.exec(ReactMount.getID(child));
+    // TODO: Node IDs are not public API; rewrite these tests.
+    var rootID = ReactDOMComponentTree.getInstanceFromNode(child)._rootNodeID;
+    var actual = idExp.exec(rootID);
     var expected = idExp.exec(expectedID);
     expect(actual).toBeTruthy();
     expect(expected).toBeTruthy();
@@ -297,14 +299,16 @@ describe('ReactIdentity', function() {
     var wrapped = <TestContainer first={instance0} second={instance1} />;
 
     wrapped = ReactDOM.render(wrapped, document.createElement('div'));
+    var div = ReactDOM.findDOMNode(wrapped);
 
-    var beforeID = ReactMount.getID(ReactDOM.findDOMNode(wrapped).firstChild);
-
+    var beforeA = div.childNodes[0];
+    var beforeB = div.childNodes[1];
     wrapped.swap();
+    var afterA = div.childNodes[1];
+    var afterB = div.childNodes[0];
 
-    var afterID = ReactMount.getID(ReactDOM.findDOMNode(wrapped).firstChild);
-
-    expect(beforeID).not.toEqual(afterID);
+    expect(beforeA).toBe(afterA);
+    expect(beforeB).toBe(afterB);
 
   });
 
diff --git a/src/renderers/shared/reconciler/__tests__/ReactInstanceHandles-test.js b/src/renderers/shared/reconciler/__tests__/ReactInstanceHandles-test.js
index 8e95862a09..17bb0b8f15 100644
--- a/src/renderers/shared/reconciler/__tests__/ReactInstanceHandles-test.js
+++ b/src/renderers/shared/reconciler/__tests__/ReactInstanceHandles-test.js
@@ -13,7 +13,6 @@
 
 var React = require('React');
 var ReactTestUtils = require('ReactTestUtils');
-var ReactMount = require('ReactMount');
 
 /**
  * Ensure that all callbacks are invoked, passing this unique argument.
@@ -74,89 +73,6 @@ describe('ReactInstanceHandles', function() {
     aggregatedArgs = [];
   });
 
-  describe('findComponentRoot', function() {
-    it('should find the correct node with prefix sibling IDs', function() {
-      var parentNode = ReactTestUtils.renderIntoDocument(
-        <div>
-          <div />
-          {[<div key="x" />]}
-        </div>
-      );
-      var childNodeB = parentNode.childNodes[1];
-
-      expect(
-        ReactMount.getNode(
-          getNodeID(childNodeB)
-        )
-      ).toBe(childNodeB);
-    });
-
-    it('should work around unidentified nodes', function() {
-      var parentNode = ReactTestUtils.renderIntoDocument(
-        <div>
-          {[<div key="x" />]}
-        </div>
-      );
-      var childNodeB = parentNode.childNodes[0];
-
-      // No ID on `childNodeA`.
-      var childNodeA = document.createElement('div');
-      parentNode.insertBefore(childNodeA, childNodeB);
-
-      expect(
-        ReactMount.getNode(
-          getNodeID(childNodeB)
-        )
-      ).toBe(childNodeB);
-    });
-
-    it('should throw if a rendered element cannot be found', function() {
-      spyOn(console, 'error');
-      var parentNode = ReactTestUtils.renderIntoDocument(
-        <table>
-          <tr />
-        </table>
-      );
-      var childNodeA = parentNode.childNodes[0];
-      var childNodeB;
-      if (childNodeA.tagName === 'TR') {
-        childNodeB = childNodeA;
-        // No ID on `childNodeA`, it was "rendered by the browser".
-        childNodeA = document.createElement('tbody');
-        childNodeA.appendChild(childNodeB);
-        parentNode.appendChild(childNodeA);
-      } else {
-        childNodeB = childNodeA.childNodes[0];
-      }
-      expect(childNodeA.tagName).toBe('TBODY');
-
-      expect(
-        ReactMount.getNode(
-          getNodeID(childNodeB)
-        )
-      ).toBe(childNodeB);
-
-      var junkID = getNodeID(childNodeB) + ':junk';
-      expect(function() {
-        ReactMount.getNode(
-          junkID
-        );
-      }).toThrow(
-        'findComponentRoot(..., ' + junkID + '): Unable to find element. ' +
-      'This probably means the DOM was unexpectedly mutated (e.g., by the ' +
-      'browser), usually due to forgetting a <tbody> when using tables, ' +
-      'nesting tags like <form>, <p>, or <a>, or using non-SVG elements in ' +
-      'an <svg> parent. Try inspecting the child nodes of the element with ' +
-      'React ID ``.'
-      );
-
-      expect(console.error.argsForCall.length).toBe(1);
-      expect(console.error.argsForCall[0][0]).toContain(
-        '<tr> cannot appear as a child of <table>'
-      );
-    });
-  });
-
   describe('getReactRootIDFromNodeID', function() {
     it('should support strings', function() {
       var test = '.s_0_1.0..1';
diff --git a/src/renderers/shared/reconciler/__tests__/ReactMultiChildReconcile-test.js b/src/renderers/shared/reconciler/__tests__/ReactMultiChildReconcile-test.js
index 778aeda9aa..5ca3e4afb1 100644
--- a/src/renderers/shared/reconciler/__tests__/ReactMultiChildReconcile-test.js
+++ b/src/renderers/shared/reconciler/__tests__/ReactMultiChildReconcile-test.js
@@ -13,8 +13,8 @@
 
 var React = require('React');
 var ReactDOM = require('ReactDOM');
+var ReactDOMComponentTree = require('ReactDOMComponentTree');
 var ReactInstanceMap = require('ReactInstanceMap');
-var ReactMount = require('ReactMount');
 
 var mapObject = require('mapObject');
 
@@ -190,7 +190,8 @@ function verifyDomOrderingAccurate(parentInstance, statusDisplays) {
   var i;
   var orderedDomIDs = [];
   for (i = 0; i < statusDisplayNodes.length; i++) {
-    orderedDomIDs.push(ReactMount.getID(statusDisplayNodes[i]));
+    var inst = ReactDOMComponentTree.getInstanceFromNode(statusDisplayNodes[i]);
+    orderedDomIDs.push(inst._rootNodeID);
   }
 
   var orderedLogicalIDs = [];
diff --git a/src/test/ReactDefaultPerf.js b/src/test/ReactDefaultPerf.js
index 24827bd295..7fdc6e518e 100644
--- a/src/test/ReactDefaultPerf.js
+++ b/src/test/ReactDefaultPerf.js
@@ -13,6 +13,7 @@
 'use strict';
 
 var DOMProperty = require('DOMProperty');
+var ReactDOMComponentTree = require('ReactDOMComponentTree');
 var ReactDefaultPerfAnalysis = require('ReactDefaultPerfAnalysis');
 var ReactMount = require('ReactMount');
 var ReactPerf = require('ReactPerf');
@@ -175,8 +176,7 @@ var ReactDefaultPerf = {
         totalTime = performanceNow() - start;
 
         if (fnName === '_mountImageIntoNode') {
-          var mountID = ReactMount.getID(args[1]);
-          ReactDefaultPerf._recordWrite(mountID, fnName, totalTime, args[0]);
+          ReactDefaultPerf._recordWrite('', fnName, totalTime, args[0]);
         } else if (fnName === 'dangerouslyProcessChildrenUpdates') {
           // special format
           args[0].forEach(function(update) {
@@ -206,7 +206,7 @@ var ReactDefaultPerf = {
           if (moduleName === 'EventPluginHub') {
             id = id._rootNodeID;
           } else if (typeof id === 'object') {
-            id = ReactMount.getID(args[0]);
+            id = ReactDOMComponentTree.getInstanceFromNode(args[0])._rootNodeID;
           }
           ReactDefaultPerf._recordWrite(
             id,