We compare the clinical course of 74 boys 10–18 years of age with Duchenne muscular dystrophy (DMD) treated (40) and not treated (34) with deflazacort. Treated boys were able to rise from supine to standing, climb stairs and walk 10 m without aids, 3–5 years longer than boys not treated. After 10 years of age, treated boys had significantly better pulmonary function than boys not treated and af...