A new contention-based demand assignment protocol (CPODA) is described. The protocol is designed to handle packetized data and voice traffic in a multiple access satellite broadcast channel, where the channel is typically shared by hundreds of earth stations. A sophisticated traffic environment is assumed, including multiple priority and delay class distinctions, variable message lengths, and an arbitrary load distribution among the stations. In addition, stations may have different receiving rate capabilities. The CPODA protocol is part of a broader research project concerned with developing protocols for a one-hop satellite network (SATNET). The CPODA and other protocols are currently undergoing experimental evaluation using an INTELSAT IV-A satellite and four earth stations in the Atlantic region.