To study the natural history of scoliosis in spinal muscular atrophy (SMA), 63 spinal radiographs of affected patients who attended the Muscle Clinic of Rizzoli Orthopaedic Institute between 1974 and 1988 were reviewed. All but one of the intermediate SMA patients, and all of the mild SMA patients who stopped walking had a scoliosis that ranged from 10 degrees to 165 degrees. Out of the 19 mild SMA patients still able to walk, 12 had a scoliosis ranging from 10 degrees to 45 degrees. Mean age at the onset of scoliosis was 4 years 4 months in intermediate SMA, and 9 years 10 months in mild SMA. Data on characteristics of the scoliotic curve are reported. The effectiveness of orthopaedic treatment in the prevention of scoliosis is discussed.