We studied 71 Japanese individuals, 42 patients (30 familial and 12 sporadic) suspected to have facioscapulohumeral muscular dystrophy (FSHD) and 29 family members, clinically and genetically using the chromosome 4qter DNA marker p13E-11. Early onset FSHD was detected in 7 patients, tortuosity of retinal arterioles and hearing impairment in 3 patients, progressive respiratory failure in 3 patients and limb-girdle type muscular weakness in 6 patients. Thirty-six (85.7%) FSHD patients, 3 asymptomatic family members and 1 of 35 healthy volunteers showed EcoRI digestion fragments shorter than 28kb. New mutations were detected in 25% of the patients with shorter EcoRI fragment. The age of disease onset appeared younger with successive generations in 6 parent-child pairs in FSHD families. We confirmed the existence of phenotypic and genetic diversities in Japanese patients with FSHD. It is still difficult to explain the phenotypic diversity merely by the size of the abnormal EcoRI fragment detected with the p13E-11 probe.