The standard regimen for prophylaxis in bilary surgery consists of three doses of a first- or second-generation cephalosporin (one pre- and two postoperatively). The purpose of our study was to compare a single dose of cefuroxime (1.5 gi.v. on call to surgery) with the standard regimen (1.5 gi.v. on call to surgery followed by two additional doses of 750 mg i.v. each, 8 and 16 h after surgery). One hundred patients participated in the study, 44 in the single-dose group and 56 in the triple-dose group. These two groups did not differ with regard to sex, risk factors, duration of surgery, etc. The incidence of infection was 9% in the single-dose group and 7% in the triple-dose group. We conclude that one dose of cefuroxime is as effective as three for biliary surgery. This regimen would reduce the risk of side effects and/or suprainfections and the emergence of resistant strains of bacteria. It is also more convenient for the nursing staff and reduces the cost by one-half.