Scoliosis associated with muscular dystrophy frequently necessitates surgical stabilization of the spine. The timing of surgery usually is based on the degree of spinal angulation. Pulmonary function, which deteriorates with age in children with muscular dystrophy, should also be an important consideration in this timing. In a retrospective study of 48 patients who underwent spinal stabilization, preoperative respiratory function tests were correlated with postoperative respiratory complications. The percentage of predicted vital capacity provided the best indicator of outcome and values of less than 30% were associated with major respiratory complications. Spinal fixation failed to arrest the decline in respiratory function in these patients, but it seemed to slow the rate of deterioration compared with preoperative changes. Evaluation of pulmonary function should play a major role in the timing of surgical intervention in muscular dystrophy.