Infection is a constant concern during perioperative period. Bacteremia occur during intervention and immediate postoperative period. They are the risk of acute complications, mainly septic shock with a high mortality rate. Escherichia coli is the germ most often found, then Enterococcus and other gram-negative germs. Diagnosis of an urinary infection is made difficult because the presence of a vesical catheter; so, 10(3) bacteria per ml. have to be considered as pathological. Two therapeutic behaviours can be considered in practice: suitable antibiotherapy in obvious infections, but sterilization of urines must not delay surgical intervention, short-time peri-operative prophylaxis cephalosporins of the 2nd or 3rd generation are most often utilized. Overseas, trimethoprim associated with sulfamides can be administrated per os every 2 hours before surgical intervention, at the time of anesthesia for example.