The goals of antibacterial prophylaxis during obstetric/gynaecological surgery are similar to those of prophylaxis during intra-abdominal surgery. The vaginal flora consists of many aerobic and anaerobic organisms, is dominated by peroxide-producing lactobacilli, and is non-pathogenic under normal conditions. Destabilization of the vaginal ecosystem, as in bacterial vaginosis (BV), causes a massive increase in the ratio of anaerobes to aerobes and is associated with a large increase in the risk of infection. The surgical procedures at most risk of postoperative infection are vaginal, abdominal and radical hysterectomy and caesarean section. Both the American College of Obstetricians and Gynecologists and the American Society of Health-System Pharmacists have recommended single-dose prophylactic protocols using a variety of agents (penicillins, cephalosporins and clindamycin). However, it remains doubtful whether prophylaxis is used widely. In Italy, such prophylaxis has proved less effective in women with BV. Accordingly, patients with confirmed BV are given topical clindamycin for 7 days leading up to surgery, in addition to the usual prophylactic regimen. Caesarean delivery carries a 5- to 20-fold greater risk of infection that normal vaginal delivery. A meta-analysis of 66 clinical studies has shown that any prophylactic regimen is effective in reducing postoperative complications. The use of prophylaxis in patients undergoing a low-risk caesarean section remain controversial.