If the thread method completes its execution, .NET will shutdown the thread gracefully. However, any unhandled exception thrown on the call stack of the thread will terminate not just the thread but also will trigger shutdown of hosting process itself. The one exception to this rule is the ThreadAbortException, which will only terminate the aborted thread. This behavior is a breaking change introduced by .NET 2.0. In contract, .NET 1.1 will only terminate the thread that encountered the unhandled exception. When porting .NET 1.1 applications to .NET 2.0, make sure that your thread methods always catch and handle any exception, otherwise you risk unplanned application termination.