diff --git a/modules/locations/HashLocation.js b/modules/locations/HashLocation.js
index 871f806174..c041fe3995 100644
--- a/modules/locations/HashLocation.js
+++ b/modules/locations/HashLocation.js
@@ -67,38 +67,33 @@ var HashLocation = {
     // Do this BEFORE listening for hashchange.
     ensureSlash();
 
-    if (_isListening)
-      return;
+    if (!_isListening) {
+      if (window.addEventListener) {
+        window.addEventListener('hashchange', onHashChange, false);
+      } else {
+        window.attachEvent('onhashchange', onHashChange);
+      }
 
-    if (window.addEventListener) {
-      window.addEventListener('hashchange', onHashChange, false);
-    } else {
-      window.attachEvent('onhashchange', onHashChange);
+      _isListening = true;
     }
-
-    _isListening = true;
   },
 
   removeChangeListener: function(listener) {
-    for (var i = 0, l = _changeListeners.length; i < l; i ++) {
-      if (_changeListeners[i] === listener) {
-        _changeListeners.splice(i, 1);
-        break;
+    _changeListeners = _changeListeners.filter(function (l) {
+      return l !== listener;
+    });
+
+    if (_changeListeners.length === 0) {
+      if (window.removeEventListener) {
+        window.removeEventListener('hashchange', onHashChange, false);
+      } else {
+        window.removeEvent('onhashchange', onHashChange);
       }
-    }
-
-    if (window.removeEventListener) {
-      window.removeEventListener('hashchange', onHashChange, false);
-    } else {
-      window.removeEvent('onhashchange', onHashChange);
-    }
 
-    if (_changeListeners.length === 0)
       _isListening = false;
+    }
   },
 
-
-
   push: function (path) {
     _actionType = LocationActions.PUSH;
     window.location.hash = Path.encode(path);
diff --git a/modules/locations/HistoryLocation.js b/modules/locations/HistoryLocation.js
index 62b945d669..ccecbddb28 100644
--- a/modules/locations/HistoryLocation.js
+++ b/modules/locations/HistoryLocation.js
@@ -38,38 +38,33 @@ var HistoryLocation = {
   addChangeListener: function (listener) {
     _changeListeners.push(listener);
 
-    if (_isListening)
-      return;
+    if (!_isListening) {
+      if (window.addEventListener) {
+        window.addEventListener('popstate', onPopState, false);
+      } else {
+        window.attachEvent('popstate', onPopState);
+      }
 
-    if (window.addEventListener) {
-      window.addEventListener('popstate', onPopState, false);
-    } else {
-      window.attachEvent('popstate', onPopState);
+      _isListening = true;
     }
-
-    _isListening = true;
   },
 
   removeChangeListener: function(listener) {
-    for (var i = 0, l = _changeListeners.length; i < l; i ++) {
-      if (_changeListeners[i] === listener) {
-        _changeListeners.splice(i, 1);
-        break;
+    _changeListeners = _changeListeners.filter(function (l) {
+      return l !== listener;
+    });
+
+    if (_changeListeners.length === 0) {
+      if (window.addEventListener) {
+        window.removeEventListener('popstate', onPopState);
+      } else {
+        window.removeEvent('popstate', onPopState);
       }
-    }
-
-    if (window.addEventListener) {
-      window.removeEventListener('popstate', onPopState);
-    } else {
-      window.removeEvent('popstate', onPopState);
-    }
 
-    if (_changeListeners.length === 0)
       _isListening = false;
+    }
   },
 
-
-
   push: function (path) {
     window.history.pushState({ path: path }, '', Path.encode(path));
     History.length += 1;
diff --git a/modules/locations/TestLocation.js b/modules/locations/TestLocation.js
index 036516765d..149c22ad08 100644
--- a/modules/locations/TestLocation.js
+++ b/modules/locations/TestLocation.js
@@ -28,8 +28,6 @@ var TestLocation = {
     updateHistoryLength();
   },
 
-  removeChangeListener: function () {},
-
   push: function (path) {
     TestLocation.history.push(path);
     updateHistoryLength();
diff --git a/modules/utils/createRouter.js b/modules/utils/createRouter.js
index 2109d21fa6..bc2dafd650 100644
--- a/modules/utils/createRouter.js
+++ b/modules/utils/createRouter.js
@@ -157,6 +157,14 @@ function createRouter(options) {
   var state = {};
   var nextState = {};
   var pendingTransition = null;
+  var changeListener = null;
+
+  function cancelPendingTransition() {
+    if (pendingTransition) {
+      pendingTransition.abort(new Cancellation);
+      pendingTransition = null;
+    }
+  }
 
   function updateState() {
     state = nextState;
@@ -192,6 +200,7 @@ function createRouter(options) {
 
       defaultRoute: null,
       notFoundRoute: null,
+      isRunning: false,
 
       /**
        * Adds routes to this router from the given children object (see ReactChildren).
@@ -317,10 +326,7 @@ function createRouter(options) {
        * hooks wait, the transition is fully synchronous.
        */
       dispatch: function (path, action, callback) {
-        if (pendingTransition) {
-          pendingTransition.abort(new Cancellation);
-          pendingTransition = null;
-        }
+        cancelPendingTransition();
 
         var prevPath = state.path;
         if (prevPath === path)
@@ -396,6 +402,11 @@ function createRouter(options) {
        * Router.*Location objects (e.g. Router.HashLocation or Router.HistoryLocation).
        */
       run: function (callback) {
+        invariant(
+          !this.isRunning,
+          'Router is already running'
+        );
+
         var dispatchHandler = function (error, transition) {
           pendingTransition = null;
 
@@ -412,7 +423,7 @@ function createRouter(options) {
           router.dispatch(location, null, dispatchHandler);
         } else {
           // Listen for changes to the location.
-          var changeListener = function (change) {
+          changeListener = function (change) {
             router.dispatch(change.path, change.type, dispatchHandler);
           };
 
@@ -421,11 +432,20 @@ function createRouter(options) {
 
           // Bootstrap using the current path.
           router.dispatch(location.getCurrentPath(), null, dispatchHandler);
+
+          this.isRunning = true;
         }
       },
 
-      teardown: function() {
-        location.removeChangeListener(this.changeListener);
+      stop: function () {
+        cancelPendingTransition();
+
+        if (location.removeChangeListener && changeListener) {
+          location.removeChangeListener(changeListener);
+          changeListener = null;
+        }
+
+        this.isRunning = false;
       }
 
     },
@@ -461,8 +481,8 @@ function createRouter(options) {
       this.setState(state);
     },
 
-    componentWillUnmount: function() {
-      router.teardown();
+    componentWillUnmount: function () {
+      router.stop();
     },
 
     render: function () {