Embryonal rhabdomyosarcomas from the nasopharynx of 2 children were examined by histochemical methods commonly applied to muscle biopsies. These stains included NAD-tetrazolium reductase (NADH-TR), succinate dehydrogenase (SDH), PAS [periodic acid-Schiff], PAS-diastase, myophosphorylase, calcium-mediated ATPase preincubated at high and low pH and oil red O. Myofibrils were easily identified with ATPase and blood vessel walls were also stained. NADH-TR clearly showed longitudinal and cross-striations that were not seen with H and E [hematoxylin and eosin] or PTAH [phosphotungstic acid-hematoxylin] stains. The modified Gomori trichrome stain additionally contributed to the recognition of myofibrils. Some techniques of muscle histochemistry applied to fresh frozen sections of tumor tissue may provide evidence of muscular differentiation in otherwise poorly differentiated sarcomas for a more accurate diagnosis of rhabdomyosarcoma.