Mechanical bowel preparation is a traditional procedure for preparing patients for colorectal surgery. This practice aims to reduce the risk of postoperative infectious complications since colonic fecal content has classically been related to stool spillage during surgery and anastomotic disruption. However, increasing evidence against its routine use can be found in experimental studies, clinical observations, prospective studies, and meta-analyses. We performed a review of the literature on mechanical bowel preparation and its consequences. There is no clear evidence that preoperative bowel cleansing reduces the septic complications of surgery and routine use of this procedure may increase anastomotic leaks and morbidity. Therefore, the results suggest that mechanical preparation is not required in elective colon and rectal surgery and that its use should be restricted to specific indications such as small nonpalpable tumors to aid their localization during laparoscopic procedures or to enable intraoperative colonoscopy. The role of mechanical bowel preparation in rectal surgery is not well defined and further trials with a larger number of patients are required.