We investigated the clinical risk factors and bacteriological examination for surgical site infection (SSI) in 144 portless endoscopic surgeries consisting of 66 clean and 78 clean-contaminated surgeries in urological diseases from April 2000 to December 2001. There were no cases of SSI in the clean surgeries. SSI occurred in 5 cases (3.5%) of clean-contaminated surgeries including total cystectomy and ileal conduit in 4 cases and total prostatectomy in 1 case. Multivariate statistical studies revealed that usage of ileum during operation and preoperative hypo-albuminemia were significant risk factors for SSI. Gram-negative rods and anaerobic bacteria were isolated from the operative wound in the total cystectomy and ileal conduit, suggesting that SSI in the operation with usage of the ileum was partially derived from contamination with endogenous bacteria, while, normal flora of the skin in the wound did not cause any post-operative SSI.