BACKGROUND. The purpose of the current study was to determine the potential therapeutic role of lymphadenectomy in women with endometrioid corpus cancer. METHODS. Demographic and clinicopathologic information were obtained from the Surveillance, Epidemiology, and End Results Program between 1988-2001. Data were analyzed using Kaplan-Meier methods and Cox proportional hazards regression. RESULTS. In all, 12,333 women (median age, 64) underwent surgical staging with lymph node assessment, including 9,009, 1,211, 1,223, and 890 with Stage I-IV disease. Over the time intervals 1988-1992, 1993-1997, and 1998-2001, the percentage of patients undergoing lymph node staging increased from 22.6%, 29.6%, to 40.9% (P < .001). In the intermediate/high-risk patients (Stage IB, Grade 3; Stage IC and II-IV; all grades), a more extensive lymph node resection (1, 2-5, 6-10, 11-20, and >20) was associated with improved 5-year disease-specific survivals across all 5 groups at 75.3%, 81.5%, 84.1%, 85.3%, and 86.8%, respectively (P < .001). For Stage IIIC-IV patients with nodal disease, the extent of node resection significantly improved the survival from 51.0%, 53.0%, 53.0%, 60.0%, to 72.0%, (P < .001). However, no significant benefit of lymph node resection in low-risk patients could be demonstrated (Stage IA, all grades; Stage IB, Grades 1 and 2 disease; P = .23). In multivariate analysis, a more extensive node resection remained a significant prognostic factor for improved survival in intermediate/high-risk patients after adjusting for other factors including age, year of diagnosis, stage, grade, adjuvant radiotherapy, and the presence of positive nodes (P < .001). CONCLUSIONS. The findings of the current study suggest that the extent of lymph node resection improves the survival of women with intermediate/high-risk endometrioid uterine cancer. © 2006 American Cancer Society.