We report a 9-year-old girl who had massive bone marrow infiltration of tumor cells at the onset of alveolar rhabdomyosarcoma. She was admitted to a surgical hospital because of abdominal pain and tumor in the buttock. Computerized tomographic scans of the pelvis revealed an abnormal mass. She was referred to our department. Hematological examination showed pancytopenia. Blood chemistry revealed hypercalcemia and hyperuricemia. Bone marrow was occupied with 100% tumor cells. Chromosome analysis of tumor cells in bone marrow revealed a specific translocation, t(2;13) (q37;q14). This finding enabled the diagnosis of a disseminated alveolar rhabdomyosarcoma to be established. She was treated with vincristine, cyclophosphamide and epirubicin, achieved a complete remission, but died of relapse 3 months after diagnosis.