OBJECTIVE: To determine if body mass index (BMI) influences tumor expression of HER-2/neu, estrogen and progesterone receptors (ER/PR), and survival in women with endometrial adenocarcinoma. METHODS: Patients diagnosed between January 1992 and December 2001 with endometrioid adenocarcinoma of the uterus were identified. Clinical and pathologic data were retrospectively collected. HER-2/neu, estrogen and progesterone receptor expression were determined by immunohistochemistry. Differences in these variables and other prognostic factors were analyzed and correlated with effect on survival. RESULTS: One-hundred-sixty-five patients were included in this analysis. Lower BMI was associated with high stage (p=0.04) and HER-2/neu expression (p=0.04). Black race, high grade, high stage and lack of ER/PR expression were all associated with decreased survival. Despite having better prognostic factors, women with a BMI >25 had a lower survival than women with a BMI <25 (p=0.36). When five-year survival rates were calculated for BMI category and stratified by prognostic factors, for almost every high risk factor, survival was lower in overweight patients. CONCLUSION: In patients with endometrioid adenocarcinoma, low BMI is associated with high stage and tumor expression of HER-2/neu. Despite better prognostic factors, overweight women experience poorer survival.