A man with Duchenne muscular dystrophy fathered two living children. He was 1 of 10 affected males in 5 generations. Clinical and genetic patterns, muscle biopsies, autopsy results, and serum enzymes were all compatible with the diagnosis of Duchenne muscular dystrophy. History, blood typing, and karyotypes indicated that he was the biologic father. This report gives confirmatory evidence that Duchenne dystrophy is transmitted as an X-linked defect.