Abstract: A contoured, corrective seat is disclosed for use in connection with a wheelchair wherein the mounting between the seat assembly and the wheelchair is of the quick-release type, and the seat assembly includes a seat frame which is adjustable as to height, depth, and angular relation between a molded buttocks supporting portion and molded back supporting portion thereof, and is also adjustable between the seat proper and the wheelchair. The buttocks and back supporting portions include separate custom molded cushions which are removably positioned in a single frame member capable of functioning as either a buttocks supporting frame or a back supporting frame. Adjustability between the two body supporting frame members allows the respective cushions to be moved relative to one another to compensate for growth in individuals, especially children.