We tested the effectiveness of prophylactic antibiotics in elective cholecystectomy in 105 patients in a single-blind, controlled randomized trial. Fifty-six patients received prophylactic antibiotics and 49 patients entered the control group. Of the patients who received prophylactic antibiotics, 3.6% had wound infections, v24.5% in the control group. The rate of wound infection in patients with positive bile cultures, diabetes, appendectomies, and choledochotomies was 24.4%, v 3.4% in the group who had cholecystectomies only, with negative bile cultures and no diabetes. We concluded that prophylactic antibiotics are effective in patients with high-risk factors such as diabetes mellitus, exploration of the choledochus, and appendectomy, and in patients with positive bile cultures.