To investigate the natural course of the spinal deformity in Duchenne muscular dystrophy (DMD) and its clinical relevance, longitudinal series of spinal radiographs and medical records of 46 patients with DMD were reviewed. The natural course of the deformity was classified into three types; type 1 (n = 21), unremittent progression of scoliosis with kyphosis; type 2 (n = 18), transition from kyphosis to lordosis before age 15 years; and type 3 (n = 7), less deformity without prominent longitudinal changes. Age at loss of ambulatory ability was not a predictor of type. Neither was the age at which the Cobb angle was 30 degrees correlated with the rate of subsequent progression. Because the spinal deformity always progresses, we consider spinal surgery justifiable in type 1, when a certain strict indication exists, such as spinal deformity > 30 degrees and age < 15 years in patients with > 35% predicted value of vital capacity. In type 2, operation may be necessary in patients in whom Cobb angle will progress unremittently. There is no surgical indication for patients with type 3.