Peer-to-peer (P2P) systems have the potential to support large-scale distributed applications by utilizing resources from a vast number of individual computers across geographically distributed areas. However, current P2P systems provide limited scheduling and resource management support to distributed applications with QoS requirements, such as timing demands. In this paper we study a utility-based scheduling approach that schedules multimedia streams in P2P systems. Our scheme determines the schedule of tasks using EDF scheduling algorithm, and adapts the delivered QoS levels of tasks according to current resource conditions at individual nodes.