Nosocomial infections are the most frequent complications observed in surgical patients. In colorectal surgery, the opening of the viscera causes the dissemination into the operative field of microorganisms originating from endogenous sources, increasing the chance of developing postoperative complications. It is reported that without antibiotic prophylaxis, wound infection after colorectal surgery develops in approximately 40% of patients. This percentage decreases to approximately 11% after antibiotic prophylaxis. Specific criteria in the choice of correct antibiotic prophylaxis have to be respected, on the basis of the microorganisms usually found in the surgical site, and on the specific hospital microbiologic epidemiology.