Surgical site infections (SSI) in colorectal surgery (anastomotic leakage, wound infection, intraabdominal abscess) are associated with increased mortality, postoperative hospital stay and costs. From a recent metanalysis and randomized clinical trial there is the emerging evidence that mechanical bowel preparation (MBP) before elective colorectal surgery is not associated with reduction of SIS, although it causes high discomfort for patients. On the same way other more recent studies show that MBP may cause an higher incidence of SIS, and that MBP may alter the bowel mucosa morphology. Other Authors report an increased incidence of anastomotic leakage requiring surgery for patients undergoing a single preoperative phosphate enema whereas but an higher cardiovascular mortality for patients undergoing MBP. Two recent studies do not clarify the usefulness of MBP for reducing SIS after colorectal surgery and one stage anastomosis. For these reasons a more precise understanding of the relationship between MBP and SIS could increase patients satisfaction and decrease unnecessary procedures and costs. At this point MBP represent the clinical standard for patients undergoing elective colorectal surgery at the European Institute of Oncology.