Objective: To estimate the prognostic significance of lymph node ratio with respect to clinicopathologic characteristics in stage IIIC endometrial cancer patients. Methods: Using data from medical records and surgery notes, we identified all consecutive patients with stage IIIC endometrial cancer who received primary surgical treatment between 1993 and 2008. Lymph node ratio is the number of metastatic lymph nodes to the total number of removed lymph nodes. Survival analyses were performed using Kaplan-Meier and Cox proportional hazard methods. Results: Two hundred sixteen patients with stage IIIC endometrial cancer were included in this multicenter study. Age, number of metastatic lymph nodes, lymph node ratio, grossly suspicious lymph nodes, histologic subtype, and cervical metastasis were associated with progression-free survival and overall survival, respectively. Patients with lymph node ratios 10% or less, more than 10-50%, and more than 50% had 5-year overall survival rates of 79.0%, 60.6%, and 35.8%, respectively (P<.001). In multivariable analysis, only lymph node ratio was associated with both progression-free survival and overall survival, respectively. Total number of removed lymph nodes and number of metastatic lymph nodes did not correlate with overall survival in the group with grossly suspicious lymph nodes, whereas lymph node ratio did. In the subgroup of 123 (56.9%) patients who had pelvic and aortic lymphadenectomies with a minimum of 10 lymph nodes removed, age and lymph node ratio were still associated with progression-free survival and overall survival, whereas total lymph nodes removed was not. Conclusion: Stratification based on lymph node ratio is useful when comprehensive lymphadenectomy is routinely performed and likely reflects metastatic nodal tumor burden. These data provide another prognostic variable in the heterogenic group of women with stage IIIC endometrial cancer.