Two sisters with muscular dystrophy of Becker-like clinical features presented. Muscle weakness was most prominent in the pelvic girdle, but in the elder sister the distal muscles of the lower extremities were also affected. The progression was different in the siblings: The older sister showed a more pronounced deterioration than the younger. The family history was negative in four generations including their brother and youngest sister. Serum creatinine kinase activities increased considerably. Electromyogram and muscle biopsy specimens revealed myopathic changes characteristic of muscular dystrophy. Chromosomal analysis confirmed normal 46,XX karyotype. DNA analysis with all cDNA probes spanning the entire dystrophin gene failed to reveal any intragenic deletion or duplication on southern blot. Immunohistochemistry for dystrophin using monoclonal antibodies against the rod and C-terminal domains showed normal continuous staining at the sarcolemma of the muscle fibers in the biopsy specimens of both patients. The results practically exclude the possibility of Xp21 myopathy, and it seems reasonable to classify these patients as having autosomal recessive childhood muscular dystrophy.