The 50-kd dystrophin-associated glycoprotein (50DAG or adhalin) in the skeletal muscle has been shown to be deficient in patients with severe childhood autosomal recessive muscular dystrophy prevalent in North Africa. To elucidate the frequency of patients having the 50DAG deficiency in a muscular dystrophy population in Japan, we immunocytochemically examined 50DAG, 43DAG, dystrophin, and utrophin. A total of 243 patients with muscular dystrophy, among 1,035 diagnostic muscle biopsies during the past 2.5 years, were analyzed. We identified five unrelated patients (three females and two males who have no family history) with 50DAG deficiency in the sarcolemma. Thus, 2.1% (5/243) of our muscular dystrophy patient population had 50DAG deficiency.