OBJECTIVE To determine if obesity is associated with prolonged surgery or more complications during and after surgery in patients undergoing robot-assisted laparoscopic prostatectomy (RALP). PATIENTS AND METHODS Between December 2003 and September 2005 data were collected prospectively for all patients undergoing RALP. Obesity was defined as a body mass index of > or = 30 kg/m2. The duration of surgery was recorded, determining the duration of steps, including overall, robotic assistance, and vesico-urethral anastomosis. In all, 285 patients had RALP by one of two surgeons; 236 were classified as not obese and 49 as obese. RESULTS The characteristics of the two groups were similar before and after RALP (mean age 60.7 vs 60.3 years, prostate-specific antigen level 7.9 vs 7.9 ng/mL, prostate weight 47.3 vs 45.3 g, length of stay 3.2 vs 3.5 days, and indwelling catheterization 8.3 vs 7.9 days). The mean duration of surgical steps was less for the non-obese than the obese group, with urethral dissection requiring 16 vs 19.3 min (P < 0.05), anastomotic time 30 vs 36 min (P < 0.01), and port closure 11 vs 14.5 min (P < 0.001), but the total duration of surgery, at 190 vs 205 min, was not significantly different (P = 0.07). In the non-obese group there were seven (3%) prolonged drain tube leaks, vs four (8%) in the obese group (P = 0.08). CONCLUSIONS Obesity was associated with longer anastomotic times, but the overall duration was similar. Overall complication rates were not significantly different. The continuing follow-up will determine if obesity predisposes patients to greater long-term morbidity after RALP.