Myogenin belongs to a family of regulatory proteins essential for muscle development. Expression of myogenin is restricted to cells of skeletal muscle origin, and appears to be inversely related to the degree of cellular differentiation. The antibody recognizes an epitope located in the amino acid region 138-158 of the myogenin protein. The antibody is a useful aid for classification of rhabdomyosarcomas and Wilms' tumors. No reactivity with Ewing's sarcoma/peripheral primitive neuroectodermal tumor, neuroblastoma, or adult skeletal muscle has been observed. Myogenin peptide from rat has been used for immunization.