A man with Duchenne muscular dystrophy fathered 2 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 karyotopes indicated that he was the biologic father. Duchenne dystrophy is transmitted as an X-linked defect.