Abstract: According to the present invention, a plurality of mattress structure components are arranged for selective assembly to provide a customized mattress structure at the point of sale to accommodate the musculoskeletal condition and interface pressure preference of the user. The mattress structure components include a perimetrical frame having a central opening and a plurality of cores which are provided in a variety of firmness and support characteristics such that various combinations of firmness and support can be selectively provided. The frame is preferably made from a relatively firm foam rubber such as a high resiliency, high density urethane foam and the plurality of cores includes air bladders, "zone foam" elements, "sculptured foam" shaped from foam blocks, and combinations thereof for filling the central opening of the perimetral frame. The mattress is also suitable for use with an articulating deck having longitudinally spaced head, seat, thighs and foot sections.