Intelligence tests were carried out on 34 boys with muscular dystrophy. The 16 who were mildly physically disabled scored significantly lower on the verbal scale (mean 85·3) of the Wechsler Intelligence Scale for Children (WISC) than on the performance scale (mean 97·6). The 18 who were moderately or markedly physically disabled showed no significant difference between their mean verbal (87·6) and performance (89·7) scores. The results are interpreted as suggesting an early and nonprogressive impairment of verbal intelligence in Duchenne muscular dystrophy.