In a controlled and blind study we were not able to identify any abnormality of erythrocytes of eight patients with Duchenne muscular dystrophy compared with seven approximately age-matched unaffected siblings (six males, one female step-sibling). Erythrocyte morphology was found to be very sensitive to various types of cell treatment. At this time, erythrocyte morphology, evaluated by the techniques used, should not be considered an established diagnostic test for the Duchenne muscular dystrophy patient or carrier.