Of sixty-four patients with Marfan's syndrome, thirty-five had scoliosis, which in 44 per cent began in the infantile and juvenile age periods. The curve patterns were double major right thoracic-left lumbar in 48 per cent and single right thoracic in 33 per cent. At the start of treatment the curves were severe (average, 72 degrees) and quite structural (average bending correction, 36 per cent). Seventy-four per cent of the thirty-five patients had back pain. Inadequately treated and untreated curves usually progressed to severe and painful deformity. Milwaukee brace treatment was generally unsuccessful because of the severity and rigidity of the curves or the poor maintenance of correction obtained. Spine fusion combined with Harrington rod instrumentation (fourteen patients) gave an average correction of 41 per cent with an average loss of 7 degrees (average follow-up, 2.3 years). Operative treatment of scoliosis is indicated in most patients with Marfan's syndrome.