Three patients, 72, 45 and 18 years old belonging to 3 successive generations presented with respiratory insufficiency. The clinical onset was at about 40 years of age in the two older patients and at 18 years in the youngest one. Serum enzymes of muscle origin were within normal range as well as leucocyte maltase activity. The muscle biopsy in all three patients showed numerous cytoplasmic (spheroid) bodies within type I muscle fibers. Familial cytoplasmic body myopathy with familial incidence has rarely been reported and still more rarely has been revealed by respiratory insufficiency in adult life.