This is one of the Windows Communication Foundation mysteries. I still don't know why the code below does not (really) work: for (int i = 0; i < 100; i++) { IMyService proxy = new ChannelFactory("MyService")... proxy.DoSomething(); // Without this line the proxy invocation fails on the 10th DoSomething() method call // ((IChannel)proxy).Close(); } When the proxy.Close() is commented, in the code above, the WCF throws the TimeoutException on the 11th proxy invocation (the variable...