A 10-month-old boy presented with a 6-week history of abdominal pain. The pain was due to a large, stage IV embryonal rhabdomyosarcoma of the urinary bladder. The rhabdomyosarcoma was found in association with neurofibromatosis 1 (NF1) manifesting multiple café au lait spots and bowing of the right calf. The diagnosis of NF1 had not been made before presentation. This case report is intended to heighten the awareness of the manifestations of NF1 and the possibility of developing a nonneuroectodermal tumor as a concomitant of NF1, and to emphasize the importance of timely diagnosis and treatment of such an NF1-associated malignancy. Reports of the epidemiologic evidence for rhabdomyosarcoma in children with NF1 are reviewed.