We investigated the prognostic value of BMI (body mass index) in Asian patients with RCC (renal cell carcinoma). We evaluated 170 Asian patients who underwent surgery for localized RCC (pathologic T1-4 tumors in the absence of nodal or distant metastases) between 1996 and 2004 at our institution. Patients were stratified by BMI: 22 or less vs. greater than 22. Overall, CSS (cancer-specific survival) and RFS (recurrence-free survival) was estimated using the Kaplan-Meier method. Multivariate analysis was performed with the Cox regression model. The mean age and BMI of all patients was 62.4 ± 11.4 yr and 23.1 ± 3.2 kg/m(2), respectively. Patients' population consisted of 114 (67.1%) men and 56 (32.9%) women. The median follow-up was 50 mo. The BMI was less than 22 in 83 (49%) patients and greater than 22 in 87 (51%). There was a trend toward worse Eastern Cooperative Oncology Group (ECOG) performance status, less likely to have an incidentaloma, higher pathological stage, and more frequent microvascular invasion with lower BMI. Only the correlations between BMI and ECOG performance status (P = 0.003) and pathological stage (P = 0.015) were statistically significant. Of other relevant factors including gender, mode of presentation, ECOG performance status, C-reactive protein, histological type, Fuhrman nuclear grade, microvascular invasion, pathological stage, and adjuvant cytokine therapy, smaller BMI remained an independent predictor for worse CSS (44.5 mo vs. 56.0 mo, P = 0.041, HR = 10.99) and RFS (43.0 mo vs. 55.0 mo, P = 0.03, HR = 2.653), but not for OS (overall survival) (46.0 mo vs. 55.5 mo, P = 0.13, HR = 2.217) on multivariate analysis. Our findings identify increasing BMI in the Asian population as an independent predictor for favorable CSS and RFS in patients with RCC treated by surgery. Further studies, including a multiinstitutional, prospective Asian cohort, are required to confirm these findings.