There have been conflicting reports of lymphocyte capping abnormalities in Duchenne muscular dystrophy (DMD). We have evaluated the original method described by Verrill et al. in a "blind" study of 24 Duchenne muscular dystrophy boys and paired age-matched control boys. We found no differences in capping between the two groups but control boys had decreased capping compared to a group of normal adult males and females. It is concluded that the initial reports of decreased capping in DMD may have been due to differences in age between the test and control groups.