The Microsoft .NET Framework 3.5 introduced the functionality to call services from Windows Workflow Foundation (WF), and to expose workflows as a Windows Communication Foundation (WCF) service. Windows Workflow 4.0 will offer exciting new correlation capabilities in this area as well. A common pattern is to have a workflow serve as the coordinator between a number of other processes (including workflows). This talk discusses how these conversations are implemented in WF 3.5 and will be implemented in 4.0, and common patterns for conversing over a long period of time, including asynchronous messaging, long-running cancellable work, managing m-of-n responses and check pointing of progress.