The use of antibacterial prophylaxis of postoperative infections is firmly established within clean-contaminated procedures. For clean procedures, prophylaxis has traditionally been reserved for operations involving foreign-body implantation. However, evidence that postoperative infections from non-prosthetic clean procedures are highly under-reported suggests that prophylaxis is also advisable, at least for some non-prosthetic procedures, such as breast surgery and herniorrhaphy. Although cefazolin is recommended by current guidelines, cefuroxime and cefamandole have a broader antimicrobial spectrum and should be preferred in clean prosthetic surgery prophylaxis. In this type of surgery glycopeptides are not recommended for routine use but may have a role for major prosthetic implantation in units with a high incidence of methicillin-resistant staphylococci. In the case of clean-contaminated procedures, cefazolin is recommended for routine use, although colorectal procedures require an agent with improved anti-anaerobic activity. In addition, experience has shown that obstetric/gynaecological, gastroduodenal and biliary tract surgery and appendectomy all require broad-spectrum antibacterial prophylaxis. Suitable agents include cefoxitin, cefotetan, ureidopenicillins and beta-lactam/beta-lactamase inhibitor combinations. The traditional surgical classification scheme needs to be replaced with a classification that additionally accounts for patient-specific risk factors. The limitations of the current scheme may partly explain why current guidelines are so seldom followed in clinical practice.