Abstract: A pneumatic mattress system includes a plurality of rigid ribs position side-by-side and hingedly interconnected so as to form a continuous overlay basis which is flexible in one direction. A plurality of pneumatic cushions is attached to each rib so as to provide a cushioned surface. The pressure of the pneumatic cushions is controlled by a main pressure control system which includes a main supply conduit with a pressurized inlet and an exhaust, both controlled by a control unit, and a pressure sensor. The pneumatic cushions are connected through a number of tubes located within the ribs to a rib control system which selectively connects them to the main supply conduit. By synchronized control of the pressure of the main supply conduit and the rib control system, the pressure within each cushion can be measured and controlled independently.