With the improvement of speed in personal computers and workstations for communication networks and communication terminals, various applications have been emerging in recent years based on multimedia communications, including stream-type media. In these communication applications, there must be a framework by which the QoS of its stream is determined and adjusted to meet its own purposes according to the user's request and the situation of the terminal and the network. When such an adaptive QoS control mechanism is built in an individual communi cation application, however, the communication application will become complicated. It is thus desirable that the adaptive QoS control mechanism should be realized as a common basis for various communication applications. This paper proposes a framework to realize an adaptive QoS control mechanism that can serve as the common basis for various communication applications, based on direct or indirect collaboration by multiple agents. The proposed framework is implemented and its operation is verified. (C) 2002 Wiley Periodicals, Inc.