The authors describe two cases of familial muscle disease, a mother and her daughter, characterized by centrally placed nuclei and a predominance of hypotrophic type 1 fibers. Clinically the patients exhibited a muscular weakness and atrophy localized mainly distally. Both showed hypertrophy of their calves. The nosological classification of the cases is uncertain; however, both are considered as examples of centronuclear myopathy with unusual clinical features.