Nodes in a mobile ad hoc network need to thwart various attacks and malicious activities. This is especially true for the ad hoc environment where there is a total lack of centralized or third-party authentication and security architectures. This paper presents a game-theoretic model to analyze intrusion detection in mobile ad hoc networks. We use game theory to model the interactions between the nodes of an ad hoc network. We view the interaction between an attacker and an individual node as a two player non-cooperative game, and construct models for such a game. Keywords Intrusion Detection, Mobile Ad hoc Networks, Game Theory A preliminary version of portions of this material was presented at the Fifth Annual IEEE Information Assurance Workshop, United States Military Academy, West Point, New York, June 2004. 1