diff --git a/scripts/bench/bench-createclass.js b/scripts/bench/bench-createclass.js
new file mode 100644
index 0000000000..99d7759491
--- /dev/null
+++ b/scripts/bench/bench-createclass.js
@@ -0,0 +1,243 @@
+React.createClass({
+  displayName: "UnimplementedView",
+  setNativeProps: function() {},
+  render: function() {},
+});
+var mixin1 = {
+  measure: function() {},
+  measureLayout: function() {},
+  setNativeProps: function() {},
+  focus: function() {},
+  blur: function() {},
+  componentWillMount: function() {},
+  componentWillReceiveProps: function() {},
+};
+React.createClass({
+  displayName: "View",
+  mixins: [mixin1],
+  viewConfig: {uiViewClassName: "RCTView", validAttributes: null},
+  statics: {AccessibilityTraits: null, AccessibilityComponentType: null},
+  propTypes: {accessible: function() {}, accessibilityLabel: function() {}, accessibilityComponentType: function() {}, accessibilityLiveRegion: function() {}, importantForAccessibility: function() {}, accessibilityTraits: function() {}, onAccessibilityTap: function() {}, onMagicTap: function() {}, testID: function() {}, onResponderGrant: function() {}, onResponderMove: function() {}, onResponderReject: function() {}, onResponderRelease: function() {}, onResponderTerminate: function() {}, onResponderTerminationRequest: function() {}, onStartShouldSetResponder: function() {}, onStartShouldSetResponderCapture: function() {}, onMoveShouldSetResponder: function() {}, onMoveShouldSetResponderCapture: function() {}, onLayout: function() {}, pointerEvents: function() {}, style: function() {}, removeClippedSubviews: function() {}, renderToHardwareTextureAndroid: function() {}, shouldRasterizeIOS: function() {}, collapsable: function() {}, needsOffscreenAlphaCompositing: function() {}},
+  render: function() {},
+});
+var mixin2 = {
+  componentWillUnmount: function() {},
+  setTimeout: function() {},
+  clearTimeout: function() {},
+  setInterval: function() {},
+  clearInterval: function() {},
+  setImmediate: function() {},
+  clearImmediate: function() {},
+  requestAnimationFrame: function() {},
+  cancelAnimationFrame: function() {},
+};
+var mixin3 = {
+  componentWillUnmount: function() {},
+  _interactionMixinHandles: {},
+  createInteractionHandle: function() {},
+  clearInteractionHandle: function() {},
+  runAfterInteractions: function() {},
+};
+var mixin4 = {
+  componentWillMount: function() {},
+  componentWillUnmount: function() {},
+  addListenerOn: function() {},
+};
+React.createClass({
+  displayName: "Navigator",
+  propTypes: {configureScene: function() {}, renderScene: function() {}, initialRoute: function() {}, initialRouteStack: function() {}, onWillFocus: function() {}, onDidFocus: function() {}, navigationBar: function() {}, navigator: function() {}, sceneStyle: function() {}},
+  statics: {BreadcrumbNavigationBar: null, NavigationBar: null, SceneConfigs: null},
+  mixins: [mixin2, mixin3, mixin4],
+  getDefaultProps: function() {},
+  getInitialState: function() {},
+  componentWillMount: function() {},
+  componentDidMount: function() {},
+  componentWillUnmount: function() {},
+  immediatelyResetRouteStack: function() {},
+  _transitionTo: function() {},
+  _handleSpringUpdate: function() {},
+  _completeTransition: function() {},
+  _emitDidFocus: function() {},
+  _emitWillFocus: function() {},
+  _hideScenes: function() {},
+  _disableScene: function() {},
+  _enableScene: function() {},
+  _onAnimationStart: function() {},
+  _onAnimationEnd: function() {},
+  _setRenderSceneToHardwareTextureAndroid: function() {},
+  _handleTouchStart: function() {},
+  _handleMoveShouldSetPanResponder: function() {},
+  _doesGestureOverswipe: function() {},
+  _deltaForGestureAction: function() {},
+  _handlePanResponderRelease: function() {},
+  _handlePanResponderTerminate: function() {},
+  _attachGesture: function() {},
+  _detachGesture: function() {},
+  _handlePanResponderMove: function() {},
+  _moveAttachedGesture: function() {},
+  _matchGestureAction: function() {},
+  _transitionSceneStyle: function() {},
+  _transitionBetween: function() {},
+  _handleResponderTerminationRequest: function() {},
+  _getDestIndexWithinBounds: function() {},
+  _jumpN: function() {},
+  jumpTo: function() {},
+  jumpForward: function() {},
+  jumpBack: function() {},
+  push: function() {},
+  _popN: function() {},
+  pop: function() {},
+  replaceAtIndex: function() {},
+  replace: function() {},
+  replacePrevious: function() {},
+  popToTop: function() {},
+  popToRoute: function() {},
+  replacePreviousAndPop: function() {},
+  resetTo: function() {},
+  getCurrentRoutes: function() {},
+  _cleanScenesPastIndex: function() {},
+  _renderScene: function() {},
+  _renderNavigationBar: function() {},
+  render: function() {},
+  _getNavigationContext: function() {},
+});
+var mixin5 = {
+  mixins: [mixin4],
+  statics: {DecelerationRate: null},
+  scrollResponderMixinGetInitialState: function() {},
+  scrollResponderHandleScrollShouldSetResponder: function() {},
+  scrollResponderHandleStartShouldSetResponder: function() {},
+  scrollResponderHandleStartShouldSetResponderCapture: function() {},
+  scrollResponderHandleResponderReject: function() {},
+  scrollResponderHandleTerminationRequest: function() {},
+  scrollResponderHandleTouchEnd: function() {},
+  scrollResponderHandleResponderRelease: function() {},
+  scrollResponderHandleScroll: function() {},
+  scrollResponderHandleResponderGrant: function() {},
+  scrollResponderHandleScrollBeginDrag: function() {},
+  scrollResponderHandleScrollEndDrag: function() {},
+  scrollResponderHandleMomentumScrollBegin: function() {},
+  scrollResponderHandleMomentumScrollEnd: function() {},
+  scrollResponderHandleTouchStart: function() {},
+  scrollResponderHandleTouchMove: function() {},
+  scrollResponderIsAnimating: function() {},
+  scrollResponderScrollTo: function() {},
+  scrollResponderScrollWithouthAnimationTo: function() {},
+  scrollResponderZoomTo: function() {},
+  scrollResponderScrollNativeHandleToKeyboard: function() {},
+  scrollResponderInputMeasureAndScrollToKeyboard: function() {},
+  scrollResponderTextInputFocusError: function() {},
+  componentWillMount: function() {},
+  scrollResponderKeyboardWillShow: function() {},
+  scrollResponderKeyboardWillHide: function() {},
+  scrollResponderKeyboardDidShow: function() {},
+  scrollResponderKeyboardDidHide: function() {},
+};
+React.createClass({
+  displayName: "ScrollView",
+  propTypes: {accessible: function() {}, accessibilityLabel: function() {}, accessibilityComponentType: function() {}, accessibilityLiveRegion: function() {}, importantForAccessibility: function() {}, accessibilityTraits: function() {}, onAccessibilityTap: function() {}, onMagicTap: function() {}, testID: function() {}, onResponderGrant: function() {}, onResponderMove: function() {}, onResponderReject: function() {}, onResponderRelease: function() {}, onResponderTerminate: function() {}, onResponderTerminationRequest: function() {}, onStartShouldSetResponder: function() {}, onStartShouldSetResponderCapture: function() {}, onMoveShouldSetResponder: function() {}, onMoveShouldSetResponderCapture: function() {}, onLayout: function() {}, pointerEvents: function() {}, style: function() {}, removeClippedSubviews: function() {}, renderToHardwareTextureAndroid: function() {}, shouldRasterizeIOS: function() {}, collapsable: function() {}, needsOffscreenAlphaCompositing: function() {}, automaticallyAdjustContentInsets: function() {}, contentInset: function() {}, contentOffset: function() {}, bounces: function() {}, bouncesZoom: function() {}, alwaysBounceHorizontal: function() {}, alwaysBounceVertical: function() {}, centerContent: function() {}, contentContainerStyle: function() {}, decelerationRate: function() {}, horizontal: function() {}, directionalLockEnabled: function() {}, canCancelContentTouches: function() {}, keyboardDismissMode: function() {}, keyboardShouldPersistTaps: function() {}, maximumZoomScale: function() {}, minimumZoomScale: function() {}, onScroll: function() {}, onScrollAnimationEnd: function() {}, onContentSizeChange: function() {}, pagingEnabled: function() {}, scrollEnabled: function() {}, scrollEventThrottle: function() {}, scrollIndicatorInsets: function() {}, scrollsToTop: function() {}, showsHorizontalScrollIndicator: function() {}, showsVerticalScrollIndicator: function() {}, stickyHeaderIndices: function() {}, snapToInterval: function() {}, snapToAlignment: function() {}, zoomScale: function() {}, onRefreshStart: function() {}},
+  mixins: [mixin5],
+  getInitialState: function() {},
+  setNativeProps: function() {},
+  endRefreshing: function() {},
+  getScrollResponder: function() {},
+  getInnerViewNode: function() {},
+  scrollTo: function() {},
+  scrollWithoutAnimationTo: function() {},
+  handleScroll: function() {},
+  _handleContentOnLayout: function() {},
+  render: function() {},
+});
+var mixin6 = {
+  componentWillUnmount: function() {},
+  setTimeout: function() {},
+  clearTimeout: function() {},
+  setInterval: function() {},
+  clearInterval: function() {},
+  setImmediate: function() {},
+  clearImmediate: function() {},
+  requestAnimationFrame: function() {},
+  cancelAnimationFrame: function() {},
+};
+React.createClass({
+  displayName: "AdsManagerTabsModalView",
+  contextTypes: {navigation: function() {}},
+  mixins: [mixin6, mixin4],
+  getDefaultProps: function() {},
+  getInitialState: function() {},
+  componentWillMount: function() {},
+  componentDidMount: function() {},
+  componentWillUnmount: function() {},
+  onTabSelect: function() {},
+  _handleConnectivityChange: function() {},
+  _onTabTap: function() {},
+  startCreateFlow: function() {},
+  render: function() {},
+  _renderTabs: function() {},
+  _onAdCreated: function() {},
+  _onRemoteNotification: function() {},
+  _setAccountFromURL: function() {},
+  _updateBadgeCount: function() {},
+  _onRetry: function() {},
+  _getUnseenNotifsCount: function() {},
+  _pushNotifPermalink: function() {},
+  _onMobileConfigsLoadDone: function() {},
+  _getAccountRoute: function() {},
+  _getNotifsRoute: function() {},
+  _getSettingsRoute: function() {},
+  _getCampaignsRoute: function() {},
+  _getNavStack: function() {},
+  _onAccountChanged: function() {},
+  _onHelpCenterRequested: function() {},
+  _onGlobalError: function() {},
+  _onGlobalErrorToastDidClose: function() {},
+  _onShowNUX: function() {},
+  _closeToastAndPopover: function() {},
+  _onTabLayout: function() {},
+  _onRootNavigationWillChange: function() {},
+  _handleOpenURL: function() {},
+  _updateAccountIDFromInLink: function() {},
+  _pushInLink: function() {},
+  _pushExternalRoute: function() {},
+  _canPushExernalRoute: function() {},
+  _hasAccountTab: function() {},
+  _hasCampaignsTab: function() {},
+  _getTabForURL: function() {},
+  _getTabForExternalRoute: function() {},
+});
+React.createClass({
+  displayName: "ActionBarButton",
+  mixins: [mixin1, mixin6],
+  propTypes: {label: function() {}, iconOnly: function() {}, imageSource: function() {}, style: function() {}, onContentMeasured: function() {}, onPress: function() {}},
+  componentDidMount: function() {},
+  render: function() {},
+});
+React.createClass({
+  displayName: "ListView",
+  mixins: [mixin5, mixin2],
+  statics: {DataSource: null},
+  propTypes: {accessible: function() {}, accessibilityLabel: function() {}, accessibilityComponentType: function() {}, accessibilityLiveRegion: function() {}, importantForAccessibility: function() {}, accessibilityTraits: function() {}, onAccessibilityTap: function() {}, onMagicTap: function() {}, testID: function() {}, onResponderGrant: function() {}, onResponderMove: function() {}, onResponderReject: function() {}, onResponderRelease: function() {}, onResponderTerminate: function() {}, onResponderTerminationRequest: function() {}, onStartShouldSetResponder: function() {}, onStartShouldSetResponderCapture: function() {}, onMoveShouldSetResponder: function() {}, onMoveShouldSetResponderCapture: function() {}, onLayout: function() {}, pointerEvents: function() {}, style: function() {}, removeClippedSubviews: function() {}, renderToHardwareTextureAndroid: function() {}, shouldRasterizeIOS: function() {}, collapsable: function() {}, needsOffscreenAlphaCompositing: function() {}, automaticallyAdjustContentInsets: function() {}, contentInset: function() {}, contentOffset: function() {}, bounces: function() {}, bouncesZoom: function() {}, alwaysBounceHorizontal: function() {}, alwaysBounceVertical: function() {}, centerContent: function() {}, contentContainerStyle: function() {}, decelerationRate: function() {}, horizontal: function() {}, directionalLockEnabled: function() {}, canCancelContentTouches: function() {}, keyboardDismissMode: function() {}, keyboardShouldPersistTaps: function() {}, maximumZoomScale: function() {}, minimumZoomScale: function() {}, onScroll: function() {}, onScrollAnimationEnd: function() {}, onContentSizeChange: function() {}, pagingEnabled: function() {}, scrollEnabled: function() {}, scrollEventThrottle: function() {}, scrollIndicatorInsets: function() {}, scrollsToTop: function() {}, showsHorizontalScrollIndicator: function() {}, showsVerticalScrollIndicator: function() {}, stickyHeaderIndices: function() {}, snapToInterval: function() {}, snapToAlignment: function() {}, zoomScale: function() {}, onRefreshStart: function() {}, dataSource: function() {}, renderSeparator: function() {}, renderRow: function() {}, initialListSize: function() {}, onEndReached: function() {}, onEndReachedThreshold: function() {}, pageSize: function() {}, renderFooter: function() {}, renderHeader: function() {}, renderSectionHeader: function() {}, renderScrollComponent: function() {}, scrollRenderAheadDistance: function() {}, onChangeVisibleRows: function() {}},
+  getMetrics: function() {},
+  getScrollResponder: function() {},
+  setNativeProps: function() {},
+  getDefaultProps: function() {},
+  getInitialState: function() {},
+  getInnerViewNode: function() {},
+  componentWillMount: function() {},
+  componentDidMount: function() {},
+  componentWillReceiveProps: function() {},
+  componentDidUpdate: function() {},
+  onRowHighlighted: function() {},
+  render: function() {},
+  _measureAndUpdateScrollProps: function() {},
+  _onContentSizeChange: function() {},
+  _onLayout: function() {},
+  _setScrollVisibleLength: function() {},
+  _updateChildFrames: function() {},
+  _maybeCallOnEndReached: function() {},
+  _renderMoreRowsIfNeeded: function() {},
+  _pageInNewRows: function() {},
+  _getDistanceFromEnd: function() {},
+  _updateVisibleRows: function() {},
+  _onScroll: function() {},
+});
diff --git a/src/isomorphic/classic/class/ReactClass.js b/src/isomorphic/classic/class/ReactClass.js
index 88c986c815..f3f545c0ae 100644
--- a/src/isomorphic/classic/class/ReactClass.js
+++ b/src/isomorphic/classic/class/ReactClass.js
@@ -402,7 +402,7 @@ function validateTypeDef(Constructor, typeDef, location) {
   }
 }
 
-function validateMethodOverride(proto, name) {
+function validateMethodOverride(isAlreadyDefined, name) {
   var specPolicy = ReactClassInterface.hasOwnProperty(name) ?
     ReactClassInterface[name] :
     null;
@@ -419,7 +419,7 @@ function validateMethodOverride(proto, name) {
   }
 
   // Disallow defining methods more than once unless explicitly allowed.
-  if (proto.hasOwnProperty(name)) {
+  if (isAlreadyDefined) {
     invariant(
       specPolicy === SpecPolicy.DEFINE_MANY ||
       specPolicy === SpecPolicy.DEFINE_MANY_MERGED,
@@ -453,6 +453,7 @@ function mixSpecIntoComponent(Constructor, spec) {
   );
 
   var proto = Constructor.prototype;
+  var autoBindPairs = proto.__reactAutoBindPairs;
 
   // By handling mixins before any other properties, we ensure the same
   // chaining order is applied to methods with DEFINE_MANY policy, whether
@@ -472,7 +473,8 @@ function mixSpecIntoComponent(Constructor, spec) {
     }
 
     var property = spec[name];
-    validateMethodOverride(proto, name);
+    var isAlreadyDefined = proto.hasOwnProperty(name);
+    validateMethodOverride(isAlreadyDefined, name);
 
     if (RESERVED_SPEC_KEYS.hasOwnProperty(name)) {
       RESERVED_SPEC_KEYS[name](Constructor, property);
@@ -483,7 +485,6 @@ function mixSpecIntoComponent(Constructor, spec) {
       // 2. Overridden methods (that were mixed in).
       var isReactClassMethod =
         ReactClassInterface.hasOwnProperty(name);
-      var isAlreadyDefined = proto.hasOwnProperty(name);
       var isFunction = typeof property === 'function';
       var shouldAutoBind =
         isFunction &&
@@ -492,10 +493,7 @@ function mixSpecIntoComponent(Constructor, spec) {
         spec.autobind !== false;
 
       if (shouldAutoBind) {
-        if (!proto.__reactAutoBindMap) {
-          proto.__reactAutoBindMap = {};
-        }
-        proto.__reactAutoBindMap[name] = property;
+        autoBindPairs.push(name, property);
         proto[name] = property;
       } else {
         if (isAlreadyDefined) {
@@ -688,14 +686,14 @@ function bindAutoBindMethod(component, method) {
  * @param {object} component Component whose method is going to be bound.
  */
 function bindAutoBindMethods(component) {
-  for (var autoBindKey in component.__reactAutoBindMap) {
-    if (component.__reactAutoBindMap.hasOwnProperty(autoBindKey)) {
-      var method = component.__reactAutoBindMap[autoBindKey];
-      component[autoBindKey] = bindAutoBindMethod(
-        component,
-        method
-      );
-    }
+  var pairs = component.__reactAutoBindPairs;
+  for (var i = 0; i < pairs.length; i += 2) {
+    var autoBindKey = pairs[i];
+    var method = pairs[i + 1];
+    component[autoBindKey] = bindAutoBindMethod(
+      component,
+      method
+    );
   }
 }
 
@@ -762,7 +760,7 @@ var ReactClass = {
       }
 
       // Wire up auto-binding
-      if (this.__reactAutoBindMap) {
+      if (this.__reactAutoBindPairs.length) {
         bindAutoBindMethods(this);
       }
 
@@ -796,6 +794,7 @@ var ReactClass = {
     };
     Constructor.prototype = new ReactClassComponent();
     Constructor.prototype.constructor = Constructor;
+    Constructor.prototype.__reactAutoBindPairs = [];
 
     injectedMixins.forEach(
       mixSpecIntoComponent.bind(null, Constructor)