?his paper presents the design and implementation of a multipoint-@multipoint multiat scheme supporting hetemgemus and flexible Qos over ATM. The objective is to mate a flexible network interfxe for supporting modem coo@ve multimedia applications requiring multicasting service as well as predictable and dynamic Qual~ty of Service (Qos). The scheme features a point-tomultipint multica$ multipoint-@multipoint multicasdynamic member join and leave and QoS negotiation and re-negotiation. We present here the architecture and implementation of the scheme and highhght the difficulties and related research issueS. Keywo~ds ATM Multicast, Multimedia Communication, Qos.