Nosocomial infections are the most frequent complications of surgical patients. Most surgical site infections (SSI) are acquired intraoperatively and arise from the flora of the patient's skin, gastrointestinal tract, or mucous membranes. Although preoperative mechanical cleansing of the bowel is considered by many surgeons a cornerstone of modern elective colorectal surgery and, in association with antibiotic prophylaxis, a fundamental component of an intestinal antisepsis program, many surgeons do not perform preoperative mechanical preparation routinely.Review of the pertinent literature.Some recent randomized trials and a Cochrane review found no proof that mechanical bowel preparation reduces the risk of complications after elective colorectal surgery. Indeed, there is some evidence that this intervention is associated with a higher rate of anastomotic leakage and wound complications.The dogma that mechanical bowel preparation is necessary before elective colorectal surgery may need to be reconsidered. On the other hand, such preparation decreases operating time by improving bowel handling during construction of the anastomosis. Moreover, it is helpful when intestinal palpation will be necessary for identification of a lesion.