Abstract: A portable folding orthopedic seat unit for use on a chair, automobile seat, or the like. A semirigid seat member is hinged to a back member. Vertical rigid support means extends from the bottom to the top of the back member and supports a back-support assembly, comprising two separate, generally elliptically-shaped, padded back-support members, spaced apart from each other, and a substantially vertically rigid and laterally flexing connecting member joining them together. The connecting member serves to transfer forces from one back-support member to the other. Releasable locking means holds the assembly at a selected vertical position on the rigid support means.