Objectives: To compare the perioperative outcomes of severely obese and nonobese patients undergoing radical perineal prostatectomy (RPP). Methods: A cohort of 71 severely obese patients, as defined by a body mass index of 35 kg/m2 or more, who underwent RPP between 1992 and 2003 was retrospectively identified. These patients were matched by age, American Society of Anesthesiologists class, and year of surgery to a cohort of 71 nonobese patients (body mass index less than 25 kg/m2). Statistical testing was performed to compare the estimated blood loss, transfusion requirements, and complication rates (primary endpoints), as well as the length of surgery, intraoperative anesthesia requirements, postoperative hematocrit level, length of stay, and surgical margin status (secondary endpoints). Results: The mean body mass index ± standard deviation of patients in the obese and nonobese group was 38.9 ± 4.7 and 22.9 ± 1.6 kg/m2 (P = 0.001), respectively. Patients were similar with regard to baseline characteristics. Obese and nonobese patients did not demonstrate significant differences in mean estimated blood loss (571 ± 391 and 494 ± 317 mL, respectively; P = 0.06), transfusion rates (2.8% and 7.0%, respectively; P = 0.45), or positive surgical margin rates (14.1% and 9.9%, respectively; P = 0.22). The overall complication rates were significantly different at 16.9% and 7.0% (P = 0.03). Conclusions: Severely obese patients undergoing RPP had blood transfusion rates similar to those of the nonobese patients. Obese RPP patients were at increased risk of surgical and anesthesia-related perioperative complications, many of which might be avoidable. Specifically, efforts should be directed toward preventing the development of lower extremity neurapraxia by minimizing the operative time and optimizing patient positioning.