A common technique for improving throughput and increasing spectrum efficiency in wireless networks is the use of header compression. Removing static, implied or redundant protocol fields by synchronizing state information between a sender and receiver reduces per-packet overhead for long lived communication flows. Previous header compression work has focused primarily on single-hop unicast traffic. In this paper we describe a multi-hop multicast header compression (MMHC) scheme applicable to mobile ad-hoc networks. MMHC provides an end-to-end solution where multicast forwarders and receivers are synchronized simultaneously and not hop-by-hop as in previous schemes. Simulation results show that the reductions in per-transmission overhead achieved provide significant gains in both throughput and latency, especially when the average payload size of packets aggregated into the communication flow is small.