A modular patient support system adapted to be quickly mounted to utility vehicles such as trucks, buses, vans or trailers, to permit emergency medical workers to rapidly transform standard utility vehicles into specialized ambulances. When not in use, the modular patient support system is easily dismounted and collapsed for warehousing. The modular patient support system comprises a base frame that is used to attach the system to a vehicle. The base frame is oriented parallel and adjacent to a side wall of the vehicle. Two telescoping litter supports are attached to the base frame by hinges having a vertical axis of rotation. The two litter supports can either be extended normal to the base frame in order to support a patient on a litter, or collapsed and folded parallel to the base frame. A seat frame is adjustably attached to the base frame using multiple connecting links. When positioned vertically, the seat bottoms serve as mounting surfaces for medical equipment. When positioned horizontally, the seat frame provides restrained seating for multiple patients. Mounting rails permit the secure attachment of equipment and for the positions of the pieces of equipment to be easily adjusted.