Abstract: Gossip-based multicast can be an effective tool for providing highly reliable and scalable message dissemination. In this paper, we consider the problem of gossiping within overlapping process groups. If each subgroup independently runs a uniform gossip protocol, then the total gossip overhead could be high for a process that is a member of many subgroups. We present a novel gossip protocol that allows individual subgroup members to trade-off update quality for gossip overhead, enabling processes to belong to several subgroups while maintaining a low total gossip overhead. Our results include a mathematical model for message dissemination under this modified gossip protocol, and an algorithm that computes gossip parameters such that all processes within a subgroup achieve their desired update quality.