A comparison of radiographic and 99mTechnetium methyldiphosphonate scintigraphic evaluations for extent of skeletal disease was made retrospectively in 17 pediatric patients with Group III and IV rhabdomyosarcoma. Thirteen children had evidence of skeletal metastases. Of these, four exhibited multiple sites of blastic as well as lytic skeletal involvement on x-rays that were not detected by bone scans: two at the time of initial diagnosis, and two at relapse in children with prior radiotherapy to involved bones. In three additional patients a greater extent of bony disease was evident on x-rays than on bone scan. Neither the pathology of the tumor, lytic versus blastic quality of the bone lesion, nor lesion size per se was found to correlate with the failure to detect them on the bone scan. Although bone scans have greater sensitivity than x-rays for the detection of metastatic bone involvement in several adult and pediatric neoplasms, in the case of rhabdomyosarcoma, the radiographic exam appears to be a more sensitive indicator in some patients and should be considered an essential study in the evaluation of skeletal involvement by this tumor.