We assessed the efficacy of preoperative antibiotic prophylaxis in a prospective trial for patients undergoing insertion of Tenckhoff catheters for continuous ambulatory peritoneal dialysis (CAPD). The prophylactic regimen was a single dose of cefazolin (500 mg) and gentamicin (80 mg) given intravenously half an hour before surgery. There was no significant difference in the number of exit site infections (8 in the antibiotic group vs. 8 in the controls) and the number of episodes of peritonitis (5 in the antibiotic group vs. 2 in the controls). Our study showed that prophylactic preoperative antibiotics did not reduce the number of exit site infections and peritonitis after the insertion of Tenckhoff catheters.