We investigated the presence of apoptosis in muscle tissues from 24 patients (average age 5.44 +/- 1.81 years) with Duchenne's muscular dystrophy by in situ tailing of nuclear fragmentation. Muscle tissue from 4 children without histologic evidence of myopathy served as normal controls. Muscle fibers positive for nuclear DNA fragmentation were determined quantitatively by counting an area of at least 400 muscle fibers. Eleven of 24 specimens showed no nuclei with DNA fragmentation, On the other hand, 0.37 +/- 0.48% of fibers in patients with Duchenne's muscular dystrophy and none in controls had DNA fragmentation (P >.05). In this study, the percentage of apoptotic nuclei was higher in Duchenne's muscular dystrophy muscle than in normal controls. However, the difference did not reach a statistically significant level, and further studies with larger control groups are warranted.