OBJECTIVES: To investigate the significance of body mass index (BMI) as an independent predictor of biochemical recurrence in men treated with surgery for clinically localized adenocarcinoma of the prostate. METHODS: A total of 1877 obese patients who underwent radical prostatectomy were matched to overweight and normal-weight patients in a 1:1 ratio on the basis of propensity scores. This resulted in an overall study population of 5631 men. Clinicopathologic characteristics and biochemical recurrence outcomes after surgery were compared between the three BMI cohorts. RESULTS: Normal-weight patients exhibited lower-grade disease compared with overweight and obese patients (P = 0.021). Lower BMI was also significantly associated with lower rates of positive surgical margins (P <0.001) and extraprostatic extension (P <0.001). Body mass index was not associated with lymph node involvement (P = 0.226) or seminal vesicle invasion (P = 0.142). Body mass index, age, biopsy Gleason score, preoperative prostate-specific antigen level, and clinical tumor stage were independent predictors of biochemical recurrence (P <0.001). CONCLUSIONS: Propensity score-based matched analyses indicate that higher BMI is associated with adverse pathologic findings and is a strong independent predictor of biochemical recurrence after radical prostatectomy. These results support the hypothesis that inherent differences may exist in the biological properties of prostate cancer in obese men compared with normal-weight men. Therefore, BMI is an important criterion to consider during subsequent decision making and counseling of patients with prostate cancer.