This paper proposes the use of reliable group communication as a complement to traditional asynchronous messaging in multi-agent systems. In particular, the mechanism of message publication on a virtually synchronous group communication channel is described and an example electronic trading scenario (the game of Pit) is used to illustrate how this form of communication supports the design of interaction protocols in which a shared perception of the order of messages is important. It is also shown that this style of messaging can be used to support the definition of social commitments based on a shared understanding of message order within a conversation. Categories and Subject Descriptors I.2.11 [Computing Methodologies]: Artificial Intelligence—Multiagent systems Keywords Reliable group communication, interaction protocols, Pit, commitments