A specific-weight chart and simple clinical tools are sufficient to obtain an accurate diagnosis of undernutrition or obesity among patients with Duchenne muscular dystrophy (DMD). The authors collected weight-for-age measures from a sample of 252 boys and anthropometric data from 109 of those boys with DMD. The data confirm the accuracy of the DMD ideal-weight chart previously proposed by Griffiths and Edwards (1988). Obesity may occur from the age of seven years; its prevalence seems to reach 54 per cent by the age of 13 years. Undernutrition occurs after the age of 14 years, involving 54 per cent of boys at about 18 years of age. Obese boys show a centralized body-fat distribution, in agreement with other obese populations.