Multimedia multiuser applications such as computer supported cooperative working, desktop multimedia conferencing, and distance education require more complex and structured communication services from the underlying communication platform than conventional applications. The call model of the communication platform defines how the underlying basic data transport objects can be structured to support more complex communication services, and how the structured objects can be managed in a consistent manner by the applications. In this paper, we present a new call model for multimedia multiuser communication platform, based on the analysis of communication requirements for diverse applications. Our call model provides better structuring capability than the existing call models, and the communication platform based on the call model will support present and future complex multimedia multiuser applications more efficiently. Detailed call control operations are also presented in this paper