diff --git a/layout/xul/base/src/nsTreeCellFrame.cpp b/layout/xul/base/src/nsTreeCellFrame.cpp
index fa6ea5c5b800..0eed3dc60798 100644
--- a/layout/xul/base/src/nsTreeCellFrame.cpp
+++ b/layout/xul/base/src/nsTreeCellFrame.cpp
@@ -31,6 +31,15 @@
 #include "nsXULAtoms.h"
 #include "nsCOMPtr.h"
 
+// Includes related to the execution of custom JS event handlers
+#include "nsIPrivateDOMEvent.h"
+#include "nsIDOMEvent.h"
+#include "nsIScriptContextOwner.h"
+#include "nsIScriptContext.h"
+#include "nsIScriptObjectOwner.h"
+#include "nsIJSScriptObject.h"
+
+static NS_DEFINE_IID(kIScriptObjectOwnerIID,      NS_ISCRIPTOBJECTOWNER_IID);
 
 static void ForceDrawFrame(nsIFrame * aFrame)
 {
@@ -165,6 +174,8 @@ nsTreeCellFrame::HandleEvent(nsIPresContext& aPresContext,
     aEventStatus = nsEventStatus_eConsumeDoDefault;
 	  if (aEvent->message == NS_MOUSE_LEFT_BUTTON_DOWN)
 		  HandleMouseDownEvent(aPresContext, aEvent, aEventStatus);
+    else if (aEvent->message == NS_MOUSE_LEFT_CLICK)
+      HandleClickEvent(aPresContext, aEvent, aEventStatus);
 	  else if (aEvent->message == NS_MOUSE_LEFT_DOUBLECLICK)
 		  HandleDoubleClickEvent(aPresContext, aEvent, aEventStatus);
   }
@@ -179,7 +190,7 @@ nsTreeCellFrame::HandleMouseDownEvent(nsIPresContext& aPresContext,
 {
   if (mIsHeader)
   {
-	  // Toggle the sort state
+	  // Nothing to do?
   }
   else
   {
@@ -193,6 +204,31 @@ nsTreeCellFrame::HandleMouseDownEvent(nsIPresContext& aPresContext,
   return NS_OK;
 }
 
+nsresult
+nsTreeCellFrame::HandleClickEvent(nsIPresContext& aPresContext, 
+									                nsGUIEvent*     aEvent,
+									                nsEventStatus&  aEventStatus)
+{
+  if (mIsHeader)
+  {
+	  // Nothing to do?
+  }
+  else
+  {
+    // Need to look for an "onItemClick" handler in the tree tag (our great-grandparent). 
+    // If one exists, then we should execute the JavaScript code in the context of the
+    // treeitem (our parent).
+    // Create a DOM event from the nsGUIEvent that occurred.
+    nsIDOMEvent* aDOMEvent;
+    NS_NewDOMEvent(&aDOMEvent, aPresContext, aEvent);
+    ExecuteDefaultJSEventHandler("onitemclick", aDOMEvent);
+    // Release the DOM event. We don't care about it any more.
+    NS_IF_RELEASE(aDOMEvent);
+  }
+  return NS_OK;
+}
+
+
 nsresult
 nsTreeCellFrame::HandleDoubleClickEvent(nsIPresContext& aPresContext, 
 									    nsGUIEvent*     aEvent,
@@ -224,6 +260,8 @@ nsTreeCellFrame::HandleDoubleClickEvent(nsIPresContext& aPresContext,
 	  }
 
 	  // Ok, try out the hack of doing frame reconstruction
+    // XXX: This needs to change
+    // XXX: Need to only do this for containers.
 	  nsCOMPtr<nsIPresShell> pShell;
     aPresContext.GetShell(getter_AddRefs(pShell));
 	  nsCOMPtr<nsIStyleSet> pStyleSet;
@@ -252,8 +290,7 @@ nsTreeCellFrame::HandleDoubleClickEvent(nsIPresContext& aPresContext,
 }
 
 
-void
-nsTreeCellFrame::Select(nsIPresContext& aPresContext, PRBool isSelected, PRBool notifyForReflow)
+void nsTreeCellFrame::Select(nsIPresContext& aPresContext, PRBool isSelected, PRBool notifyForReflow)
 {
 	nsCOMPtr<nsIAtom> kSelectedCellAtom(dont_AddRef(NS_NewAtom("selectedcell")));
   nsCOMPtr<nsIAtom> kSelectedAtom(dont_AddRef(NS_NewAtom("selected")));
@@ -276,3 +313,106 @@ nsTreeCellFrame::Select(nsIPresContext& aPresContext, PRBool isSelected, PRBool
 
   NS_IF_RELEASE(pParentContent);
 }
+
+const char* cEvent[] = {"event"};
+
+void nsTreeCellFrame::ExecuteDefaultJSEventHandler(const nsString& eventName,
+                                                   nsIDOMEvent* aDOMEvent)
+{
+  // Get our parent, grandparent, and great-grandparent nodes
+  nsCOMPtr<nsIContent> treeitem;
+  nsCOMPtr<nsIContent> treebody;
+  nsCOMPtr<nsIContent> tree;
+
+  mContent->GetParent(*(getter_AddRefs(treeitem)));
+  treeitem->GetParent(*(getter_AddRefs(treebody)));
+  treebody->GetParent(*(getter_AddRefs(tree)));
+
+  // See if the attribute is even present on the tree node.
+  PRInt32 namespaceID;
+  tree->GetNameSpaceID(namespaceID);
+  nsIAtom* eventNameAtom = NS_NewAtom(eventName);
+  nsString codeText;
+  nsresult rv = tree->GetAttribute(namespaceID, eventNameAtom, codeText);
+  NS_IF_RELEASE(eventNameAtom);
+
+  if (rv == NS_CONTENT_ATTR_HAS_VALUE)
+  {
+    // Compile/execute the JavaScript code in the context of the treeitem.
+    // XXX: Make this code more robust. Check for null pointers.
+
+    // Retrieve our document.
+    nsCOMPtr<nsIDocument> document;
+    rv = tree->GetDocument(*getter_AddRefs(document));
+    if (rv != NS_OK)
+      return;
+
+    // Retrieve the script context owner for the document.
+    nsIScriptContextOwner* scriptContextOwner = document->GetScriptContextOwner();
+
+    // Retrieve the script context from the owner.
+    nsCOMPtr<nsIScriptContext> scriptContext;
+    rv = scriptContextOwner->GetScriptContext(getter_AddRefs(scriptContext));
+    if (rv != NS_OK)
+      return;
+
+    NS_IF_RELEASE(scriptContextOwner);
+
+    // The TREEITEM is considered to be the script object owner.
+    nsIScriptObjectOwner* scriptObjectOwner;
+    if (treeitem->QueryInterface(kIScriptObjectOwnerIID, (void**) &scriptObjectOwner) != NS_OK)
+      return;
+    
+    // Obtain the script object from its owner.
+    JSObject* jsObject;
+    rv = scriptObjectOwner->GetScriptObject(scriptContext, (void**)&jsObject);
+    NS_IF_RELEASE(scriptObjectOwner);
+    if (rv != NS_OK)
+      return;
+
+    // Obtain the JS native context
+    JSContext* jsContext = (JSContext*)scriptContext->GetNativeContext();
+
+    nsString lowerEventName;
+    eventName.ToLowerCase(lowerEventName);
+
+    char* charName = lowerEventName.ToNewCString();
+
+    if (charName)
+    {
+      // Compile the function.
+      JS_CompileUCFunction(jsContext, jsObject, charName,
+		           1, cEvent, (jschar*)codeText.GetUnicode(), codeText.Length(),
+		           nsnull, 0);
+      
+      // Execute the function.
+      jsval funval, result;
+      jsval argv[1];
+      
+      if (!JS_LookupProperty(jsContext, jsObject, charName, &funval)) {
+        delete charName;
+        return;
+      }
+
+      delete charName;
+
+      if (JS_TypeOfValue(jsContext, funval) != JSTYPE_FUNCTION) {
+        return;
+      }
+
+      JSObject* aEventObj;
+      nsIScriptContext *scriptCX = (nsIScriptContext *)JS_GetContextPrivate(jsContext);
+      if (NS_OK != NS_NewScriptEvent(scriptCX, aDOMEvent, nsnull, (void**)&aEventObj)) {
+        return;
+      }
+
+      argv[0] = OBJECT_TO_JSVAL(aEventObj);
+      if (PR_TRUE == JS_CallFunctionValue(jsContext, jsObject, funval, 1, argv, &result)) {
+	      if (JSVAL_IS_BOOLEAN(result) && JSVAL_TO_BOOLEAN(result) == JS_FALSE) {
+          return; // XXX: Denoted failure. Do I care?
+        }
+        return; // XXX: Denoted success.
+      }
+    }
+  } // XXX: Am I missing out on some necessary cleanup?
+}
\ No newline at end of file
diff --git a/layout/xul/base/src/nsTreeCellFrame.h b/layout/xul/base/src/nsTreeCellFrame.h
index fef6de963814..1d3b28c21e09 100644
--- a/layout/xul/base/src/nsTreeCellFrame.h
+++ b/layout/xul/base/src/nsTreeCellFrame.h
@@ -53,14 +53,19 @@ protected:
   virtual ~nsTreeCellFrame();
 
   nsresult HandleMouseDownEvent(nsIPresContext& aPresContext, 
-								nsGUIEvent*     aEvent,
-							    nsEventStatus&  aEventStatus);
+								                nsGUIEvent*     aEvent,
+							                  nsEventStatus&  aEventStatus);
 
   nsresult HandleDoubleClickEvent(nsIPresContext& aPresContext, 
-								  nsGUIEvent*     aEvent,
-							      nsEventStatus&  aEventStatus);
+								                  nsGUIEvent*     aEvent,
+							                    nsEventStatus&  aEventStatus);
+
+  nsresult HandleClickEvent(nsIPresContext& aPresContext, 
+								            nsGUIEvent*     aEvent,
+							              nsEventStatus&  aEventStatus);
+
+  void ExecuteDefaultJSEventHandler(const nsString& eventName, nsIDOMEvent* aDOMEvent);
 
-  
 protected:
   // Data members
   PRBool mIsHeader; // Whether or not we're a column header