Antibiotic prophylaxis is highly effective in prevention of postoperative infection. The aim is bacterial growth inhibition during operative procedure. To avoid side-effects, such as increase of bacterial resistant strains and modification of patient flora, some accurate rules are relevant and among them most important are: 1) never last more than 24 hours; 2) choose molecule active against bacteria generally responsible of infections according to the type of operation, but not used in therapeutic field; 3) of crucial importance is the timing of administration: it must start before operation, ideally 30 to 60 minutes before incision. Antibiotic prophylaxis cost must be considered as it accounts for more than 30% of total antibiotic use in hospital. (C) 2013 Elsevier Masson SAS. All rights reserved.