I have an ASP.NET 3.5 WebForm that leverages the frameworks Page.ClientScript.GetCallbackEventReference() method and I'd like some of the calls to be synchronous. Now, the documentation says that the 5th parameter (see below) controls this. Specifically, when you pass 'false' it's supposed to be a non-asynchronous call. However, regardless if it's true or false, it still processes the call asynchronously. Page.ClientScript.GetCallbackEventReference(this, "arg", "ReceiveServerData", "context",false); Is there a work-around for this or perhaps I'm doing something wrong? Thanks in advance for the assistance!