A randomized control clinical study was conducted to compare the effectiveness of prophylactic ampicillin/sulbactam in preventing wound infection after elective colorectal surgery with a combination of gentamicin and metronidazole. Over a 2-year period, 143 patients were recruited, but 15 patients were subsequently excluded due to the use of additional antibiotics for the treatment of pulmonary or urinary infection or early postoperative death without wound infection. Of the 128 evaluable patients, six of the 63 patients (9.5%) in the ampicillin/sulbactam group and seven of the 65 patients (10.7%) in the gentamicin and metronidazole group developed wound infection. We conclude that prophylactic ampicillin/sulbactam is effective in reducing the risk of wound infection following colorectal surgery.