The prophylactic use of antimicrobial agents is recommended for the prevention of numerous postoperative infections. Except for oral bowel preparations, antimicrobial prophylaxis should be limited to the operative period. Prolonged perioperative prophylaxis has not been shown to enhance effectiveness. The possibilities for toxicity, resistant superinfections and rising costs are discussed. This article provides an overview together with the standards of antimicrobial prophylaxis in abdominal surgery, principles of antibiotic administration and the choice of appropriate agents.