Scalability problems, which arise when the Real Time Control Protocol (RTCP) is used in large multicast groups, include: increased feedback delay, increased storage state at every member, and ineffective RTCP bandwidth usage. This paper presents a Scalable RTCP (S-RTCP). S-RTCP is based on a hierarchical structure in which members are grouped into local regions. For every region, there is an Aggregator (AG) which receives the feedback Receiver Reports (RRs) of the local members, summarizes important information in the RRs, derives some statistics, and sends them to a Manager. The Manager performs additional statistical analysis to monitor the transmission quality and to identify regions of high congestion.A simulation of S-RTCP using the Network Simulator (NS) shows that S-RTCP alleviates some of RTCP scalability problems. Consequently, the feedback provides timely and useful QoS information required for network monitors and for adaptive applications. The main contribution of this paper is the presentation of the simulations' details and performance analysis that show the advantages of using S-RTCP over original RTCP.