A 16-year-old boy presented with paresthesias and weakness of the right thigh. A computerized axial tomography scan identified a mass within the right psoas muscle, and a needle biopsy showed a primitive neuroectodermal tumor, which did not respond to two courses of chemotherapy (Adriamycin, vincristine, and cytoxan). An anatomic resection of the psoas muscle and femoral nerve was performed and radiotherapy administered. The boy remains ambulatory and free of disease 2.5 years after resection.