ABSTRACT Objective: To investigate the relationship between the pretreatment body mass index (BMI) and the clinical outcomes in patients with localized stage I - III renal cell carcinoma (RCC) surgically treated. Materials and Methods: From January 2000 to December 2012, 798 patients with stage I - III RCC were recruited from First Affiliated Hospital and Cancer Center of Sun Yat - Sen University. Patients were divided into two groups of BMI < 25 kg / m2 or BMI ≥ 25 kg / m2 according to the World Health Organization classifications for Asian populations. The differences in the long-term survival of these two BMI groups were analyzed. Results: The 5 - year failure - free survival rates for BMI < 25 kg / m2 and BMI ≥ 25 kg / m2 groups were 81.3% and 93.3%, respectively (P = 0.002), and the 5 - year overall survival rates were 82.5% and 93.8%, respectively (P = 0.003). BMI was a favored prognostic factor of overall survival and failure - free survival in a Cox regression model. Conclusions: Pretreatment body mass index was an independent prognostic factor for Chinese patients surgically treated, localized stage I - III RCC.