A theoretical approach is presented to the quantificaiton of potential cross-country performance limits of an active suspension system. A pitch-plane representation of a wheeled vehicle is used along with the assumption of ideal actuators and perfect terrain knowledge. The geometrical constraints on possible chassis motion imposed by the vehicle and terrain geometry are formulated. Algorithms are developed to determine the optimal (in terms of vehicle ride) chassis vertical and pitch motion trajectories as well as vehicle ride limiting speed as a function of both terrain roughness and allowable suspension travel. Finally, possible active suspension implementation schemes for approaching these ideal performance limits are discussed.