Web Services are the state-of-the-art realization of a service-oriented architecture. While there is an agreed standard to describe the interface of services (WSDL) as well as an agreed standard to describe the behavior of a single process (WS-BPEL), there is no agreed standard to describe choreographies. In this paper, we give an overview about existing approaches to model choreographies and present one approach based on WS-BPEL in detail.