The need for a pretreatment staging system to accurately assess programs of therapy for the various sites and stages of childhood rhabdomyosarcoma has become apparent as detailed analyses of many factors affecting prognosis and treatment choices have been accomplished through the national cooperative trial, the Intergroup Rhabdomyosarcoma Study (IRS). Initiated in 1972, the IRS has thus far used a clinicopathologic grouping system that is based heavily on therapeutic decisions, particularly on whether or not excision is accomplished and the extent of such an operation. The major problem with this and several other staging classifications now in use is that they depend on pathologic data obtained after surgical treatment has been initiated or rejected. In addition, they do not consider histologic variations of this neoplasm which may be important in estimating prognosis. The large body of clinical data now accumulated in the IRS has provided an excellent opportunity for developing a database for evaluating the International Union Against Cancer (UICC) pretreatment staging system and also the potential for using histologic categories in the staging process. The records of 505 eligible patients entered into the IRS between 1978 and 1982 were used to determine the prognostic impact of a number of pretreatment factors. These included local invasiveness of the primary neoplasm on clinical examination, tumor size, clinical status of regional nodes, clinical or radiologic evidence of distant metastases, and favorable or unfavorable histologic categories. A retrospective assessment of the relationship of these pretreatment observations to survival experience has been carried out. This retrospective study indicates definite prognostic significance for all of the individual factors used on the UICC system except clinical status of regional nodes. Also, these data serve as a basis for considering the possibility of including favorable v unfavorable histology in the pretreatment staging system now being tested prospectively in the ongoing IRS protocols.