The improvement in survival rates for Ewing’s sarcoma by aggressive use of adjuvant chemotherapy has provided an opportunity to evaluate a number of prognostic factors for this improving situation. Analysis of results in 66 consecutive cases admitted to the Radiation Branch of the National Cancer Institute indicates the importance of considering these factors in future treatment planning. In addition to the presence or absence of clinical metastasis at the time of diagnosis, the site of the primary lesion, the age at diagnosis, and the presence of systemic symptoms (particularly fever) have proved to be reliable indicators of subsequent survival experience. Other factors of potential importance, but requiring further evaluation and experience, include lactic dehydrogenase levels, duration of symptoms, erythrocyte sedimentation rate, total white blood cell and total lymphocyte levels, platelet determinations, tissue hypersensitivity reactions, and measurements of immune competence. Sex, if adjusted to growth and maturation, has little effect except in relation to menarche, with potential relapse occurring in association with the onset of menstruation. The importance of consideration of these factors in the planning of future treatment regimens is readily apparent, and emphasizes the need for centralization of treatment of Ewing’s sarcoma where such evaluation will be possible in sufficient numbers of patients to help determine the optimum adjuvant therapy regimen for each category of patient and eventually for each individual patient.