An understanding of the patterns of spread and prognostic factors influencing survival is necessary to develop rational treatment programs for patients with endometrial cancer. The most important risk factors include the stage of tumor, status of pelvic lymph nodes, depth of myometrial penetration, tumor grade, cell type, and patient age. Because of the inherent inaccuracies of staging based on pelvic examination and the inability to assess the status of lymph nodes or myometrial penetration clinically, errors in management often result when radiation therapy is delivered prior to operation. Therefore, a rationale is offered for primary operative management of patients with Stage I disease, with consideration of adjunctive radiation therapy following operation based on extend of disease and a thorough evaluation of the high-risk factors. It is suggested that patients with more advanced stages of disease be considered for pretreatment operative evaluation. Data are presented which refute theoretical objections to this approach.