The association of tumor size and lymph node metastasis in endometrial cancer clinically confined to the uterus was evaluated in 91 patients. Other factors possibly associated with lymph node metastasis were also analyzed. Tumor size was independently associated with lymph node metastasis when analyzed by multivariate analysis (P = .022). Patients with tumors less than or equal to 2 cm in diameter had only a 5.7% incidence of lymphatic metastases. When tumors exceeded 2 cm in diameter or involved the entire endometrial surface, metastases occurred in 21.7 and 40.0% of patients, respectively. Measuring tumor size at surgery, or possibly preoperatively by hysteroscopy, will help predict which patients are at increased risk for lymph node metastasis. There were no lymph node metastases in patients with tumors less than or equal to 2 cm in diameter and invasion of less than half of the myometrium. For these patients, extended surgical staging with pelvic and aortic lymph node biopsies may not be indicated.