While multi-player online games are very successful, their fast deployment suffers from their server-based architecture. Indeed, servers both limit the scalability of the games and increase deployment costs. However, they make it easier to control the game (e.g. by preventing cheating and providing support for billing). Peer-to-peer, i.e. transfer of the game functions on each each player’s machine, is an attractive communication model for online gaming. We investigate here the challenges of peer-to-peer gaming, hoping that this discussion will generate a broader interest in the research community. Categories and Subject Descriptors C.2.2 [Computer Communication Networks]: Distributed Systems General Terms Design, Performance, Security Keywords Peer-to-Peer, Overlay Online-gaming, Security