Abstract. IP multicast suffers from scalability problem with the number of concurrently active multicast groups, while scalability of QoS multicast is even further from being solved. In this paper, we propose an approach to reduce multicast forwarding state and provision multicast with QoS guarantees. In our approach, multiple groups are forced to share a single delivery tree. We discuss the advantages and some implementation issues of our approach, and conclude that it is feasible and promising. We then describe how to use our approach to provision scalable QoS multicast. Finally, we define metrics to quantify state reduction and use simulations to show how our scheme achieves state reduction. These initial simulation results suggest that our method can reduce multicast state significantly.