diff --git a/src/core/ReactPropTypes.js b/src/core/ReactPropTypes.js
index 753d9d73b3..3bb52ffabc 100644
--- a/src/core/ReactPropTypes.js
+++ b/src/core/ReactPropTypes.js
@@ -81,6 +81,7 @@ var Props = {
   string: createPrimitiveTypeChecker('string'),
 
   oneOf: createEnumTypeChecker,
+  oneOfType: createUnionTypeChecker,
 
   instanceOf: createInstanceTypeChecker
 
@@ -89,13 +90,19 @@ var Props = {
 var ANONYMOUS = '<<anonymous>>';
 
 function createPrimitiveTypeChecker(expectedType) {
-  function validatePrimitiveType(propValue, propName, componentName, location) {
+  function validatePrimitiveType(
+    shouldThrow, propValue, propName, componentName, location
+  ) {
     var propType = typeof propValue;
     if (propType === 'object' && Array.isArray(propValue)) {
       propType = 'array';
     }
+    var isValid = propType === expectedType;
+    if (!shouldThrow) {
+      return isValid;
+    }
     invariant(
-      propType === expectedType,
+      isValid,
       'Invalid %s `%s` of type `%s` supplied to `%s`, expected `%s`.',
       ReactPropTypeLocationNames[location],
       propName,
@@ -109,9 +116,15 @@ function createPrimitiveTypeChecker(expectedType) {
 
 function createEnumTypeChecker(expectedValues) {
   var expectedEnum = createObjectFrom(expectedValues);
-  function validateEnumType(propValue, propName, componentName, location) {
+  function validateEnumType(
+    shouldThrow, propValue, propName, componentName, location
+  ) {
+    var isValid = expectedEnum[propValue];
+    if (!shouldThrow) {
+      return isValid;
+    }
     invariant(
-      expectedEnum[propValue],
+      isValid,
       'Invalid %s `%s` supplied to `%s`, expected one of %s.',
       ReactPropTypeLocationNames[location],
       propName,
@@ -123,9 +136,15 @@ function createEnumTypeChecker(expectedValues) {
 }
 
 function createInstanceTypeChecker(expectedClass) {
-  function validateInstanceType(propValue, propName, componentName, location) {
+  function validateInstanceType(
+    shouldThrow, propValue, propName, componentName, location
+  ) {
+    var isValid = propValue instanceof expectedClass;
+    if (!shouldThrow) {
+      return isValid;
+    }
     invariant(
-      propValue instanceof expectedClass,
+      isValid,
       'Invalid %s `%s` supplied to `%s`, expected instance of `%s`.',
       ReactPropTypeLocationNames[location],
       propName,
@@ -137,28 +156,64 @@ function createInstanceTypeChecker(expectedClass) {
 }
 
 function createChainableTypeChecker(validate) {
-  function createTypeChecker(isRequired) {
-    function checkType(props, propName, componentName, location) {
-      var propValue = props[propName];
-      if (propValue != null) {
-        // Only validate if there is a value to check.
-        validate(propValue, propName, componentName || ANONYMOUS, location);
-      } else {
-        invariant(
-          !isRequired,
-          'Required %s `%s` was not specified in `%s`.',
-          ReactPropTypeLocationNames[location],
-          propName,
-          componentName || ANONYMOUS
-        );
+  function checkType(
+    isRequired, shouldThrow, props, propName, componentName, location
+  ) {
+    var propValue = props[propName];
+    if (propValue != null) {
+      // Only validate if there is a value to check.
+      return validate(
+        shouldThrow,
+        propValue,
+        propName,
+        componentName || ANONYMOUS,
+        location
+      );
+    } else {
+      var isValid = !isRequired;
+      if (!shouldThrow) {
+        return isValid;
+      }
+      invariant(
+        isValid,
+        'Required %s `%s` was not specified in `%s`.',
+        ReactPropTypeLocationNames[location],
+        propName,
+        componentName || ANONYMOUS
+      );
+    }
+  }
+
+  var checker = checkType.bind(null, false, true);
+  checker.weak = checkType.bind(null, false, false);
+  checker.isRequired = checkType.bind(null, true, true);
+  checker.weak.isRequired = checkType.bind(null, true, false);
+  checker.isRequired.weak = checker.weak.isRequired;
+
+  return checker;
+}
+
+function createUnionTypeChecker(arrayOfValidators) {
+  return function(props, propName, componentName, location) {
+    var isValid = false;
+    for (var ii = 0; ii < arrayOfValidators.length; ii++) {
+      var validate = arrayOfValidators[ii];
+      if (typeof validate.weak === 'function') {
+        validate = validate.weak;
+      }
+      if (validate(props, propName, componentName, location)) {
+        isValid = true;
+        break;
       }
     }
-    if (!isRequired) {
-      checkType.isRequired = createTypeChecker(true);
-    }
-    return checkType;
-  }
-  return createTypeChecker(false);
+    invariant(
+      isValid,
+      'Invalid %s `%s` supplied to `%s`.',
+      ReactPropTypeLocationNames[location],
+      propName,
+      componentName || ANONYMOUS
+    );
+  };
 }
 
 module.exports = Props;
diff --git a/src/core/__tests__/ReactPropTypes-test.js b/src/core/__tests__/ReactPropTypes-test.js
index cdea401015..94e3c4b5f1 100644
--- a/src/core/__tests__/ReactPropTypes-test.js
+++ b/src/core/__tests__/ReactPropTypes-test.js
@@ -84,6 +84,12 @@ describe('Primitive Types', function() {
       '`testComponent`.'
     );
   });
+
+  it("should have a weak version that returns true/false", function() {
+    expect(typeCheck(Props.string.weak, null)()).toEqual(true);
+    expect(typeCheck(Props.string.weak.isRequired, null)()).toEqual(false);
+    expect(typeCheck(Props.string.isRequired.weak, null)()).toEqual(false);
+  });
 });
 
 describe('Enum Types', function() {
@@ -115,6 +121,13 @@ describe('Enum Types', function() {
     expect(typeCheck(Props.oneOf(['red', 'blue']), null)).not.toThrow();
     expect(typeCheck(Props.oneOf(['red', 'blue']), undefined)).not.toThrow();
   });
+
+  it("should have a weak version that returns true/false", function() {
+    var checker = Props.oneOf(['red', 'blue']);
+    expect(typeCheck(checker.weak, null)()).toEqual(true);
+    expect(typeCheck(checker.weak.isRequired, null)()).toEqual(false);
+    expect(typeCheck(checker.isRequired.weak, null)()).toEqual(false);
+  });
 });
 
 describe('Instance Types', function() {
@@ -148,3 +161,48 @@ describe('Instance Types', function() {
     expect(typeCheck(Props.instanceOf(Person), new Engineer())).not.toThrow();
   });
 });
+
+describe('Union Types', function() {
+  beforeEach(function() {
+    require('mock-modules').dumpCache();
+  });
+
+  it('should throw if none of the types are valid', function() {
+    var checker = Props.oneOfType([
+      Props.string,
+      Props.number
+    ]);
+    expect(typeCheck(checker, [])).toThrow(
+      'Invariant Violation: Invalid prop `testProp` ' +
+      'supplied to `testComponent`.'
+    );
+
+    checker = Props.oneOfType([
+      Props.string.isRequired,
+      Props.number.isRequired
+    ]);
+    expect(typeCheck(checker, null)).toThrow(
+      'Invariant Violation: Invalid prop `testProp` ' +
+      'supplied to `testComponent`.'
+    );
+  });
+
+  it('should not throw if one of the types are valid', function() {
+    var checker = Props.oneOfType([
+      Props.string,
+      Props.number
+    ]);
+    expect(typeCheck(checker, null)).not.toThrow();
+    expect(typeCheck(checker, 'foo')).not.toThrow();
+    expect(typeCheck(checker, 123)).not.toThrow();
+
+    checker = Props.oneOfType([
+      Props.string,
+      Props.number.isRequired
+    ]);
+    expect(typeCheck(checker, null)).not.toThrow();
+    expect(typeCheck(checker, 'foo')).not.toThrow();
+    expect(typeCheck(checker, 123)).not.toThrow();
+  });
+
+});