Absbact-In this paper we present a system for IP based networks which allows Policy based Handover between different access network technologies. The policy rules for selection of the access network are provided by the networklservice provider. An Interface Selection Subsystem on the mobile terminal triggers the handover according to these policy rules, and a Service Subsystem initiates adaptation of the media stream to match the network resource availability. We provide performance measnremen& to analyze the handover behaviour of our system during a running video session. These measurements show that with the proper intenvorking between interface selection in the mobile terminal and media adaptation in the video server, an almost seamless Policy based Handover between heterogeneous wireless networks is possible.