WCF enables disconnected work: the client posts messages to a queue, and the service processes them. Such interaction enables different possibilities from those presented so far and, in turn, a different programming model. This chapter starts by showing you how to set up and configure simple queued services, and then focuses on aspects such as transactions, instance management, and failures, and their impact on both the business model of the service and its implementation. The chapter ends with my solution for a response service and a discussion of using the HTTP bridge for queued calls over the Internet.