We reviewed the incidence and severity of scoliosis in 37 patients with the intermediate type and 26 with the mild type of spinal muscular atrophy. In the intermediate type, scoliosis has an early onset and rapid progression before puberty, and a spinal fusion will be needed in virtually all cases. This rapid progression occurred despite routine use of a spinal brace. Hip dislocation was frequently present but, in most cases, was secondary to the pelvic tilt and did not contribute to the scoliosis. In the mild type, the scoliosis was more variable. In the 30% of patients who had scoliosis, progression was rapid during puberty but only in those who had lost ambulation. Of the four children with the intermediate type and the seven with the mild type who walked in light-weight orthoses, progression of scoliosis was slow, except in those who had lost ambulation. The ultimate effect of walking in orthoses is difficult to assess because of small numbers, but it seems to slow or at least delay progressive scoliosis.