Purpose: To evaluate the efficacy of antibiotic prophylaxis and determine the risk factors of infectious complications after transurethral surgery of the prostate. Materials and Methods: Seven hundred and seventy-two patients who underwent transurethral resection of the prostate (TURP) or holmium laser enucleation of the prostate (HOLEP) were reviewed. Of these, this study enrolled 643 patients without bacteriuria who had not received antibiotics for urinary tract infections for two weeks before surgery. The patients were divided into two groups according to the duration of the antibiotics (Group 1: less than one day, n=396 vs. Group 2: more than one day, n=247). Results: The overall incidence of postoperative infectious complications in 643 patients was 5.0% (32/643). When postoperative infectious complications were compared according to the duration of the antibiotics (Group 1 vs. Group 2), the infectious complications rates were 5.6% (22/396) vs. 4.0% (10/247), respectively (p=0.393). When postoperative infectious complications were compared according to the duration of antibiotics (Group 1 vs. Group 2) in the TURP and HOLEP groups, the infectious complications rates were 6.3% (12/192) vs. 1.0% (1/103) (p=0.035) and 4.9% (10/203) vs. 6.0% (8/134) (p=0.677), respectively. The ...