The present invention features an all terrain, four-wheeled vehicle frame for carrying at least two passengers in a side-by-side riding configuration, comprising a rigid, tubular frame body which provides for a forward passenger compartment having structural support members for carrying a pair of seats for the side-by-side passengers and a rearward engine compartment configured for receiving an engine, power train, and transmission for driving wheels of the vehicle. The vehicle frame also includes a vertical, load-bearing truss member extending generally along a longitudinal, central axis of the vehicle within the passenger compartment, the truss member forming a load-bearing structural member between the pair of seats.