In the first half of the 20th century, mortality from colon and rectal surgery often exceeded 20%, 1 mainly attributed to sepsis. Modern surgical techniques and improved perioperative care have significantly lowered the mortality rate. Infectious complications, however, still are a major cause of morbidity in colorectal surgery, leading to increased cost, prolonged hospital stay, and occasional mortality. 2 Mechanical bowel preparation is aimed at cleaning the large bowel of fecal content, thereby reducing the rate of infectious complications following surgery. Traditionally, bowel cleansing was achieved using enemas in combination with oral laxatives. 3 More recently, oral cathartic agents to induce diarrhea and cleanse the bowel from solid feces were developed. These new bowel preparation agents, such as polyethylene glycol and sodium phosphate, provide superior cleansing compared to the more traditional methods 4–6 and are used by most surgeons in preparation for colorectal surgery. 7–9 The practice of bowel cleansing before colorectal surgery has became a surgical dogma, and primary colonic anastomosis is considered unsafe in the face of an unprepared bowel. There is, however, a paucity of data showing that mechanical bowel preparation by itself, separately from other operative and perioperative measures, actually reduces the rate of infectious complications. In urgent colon surgery for penetrating trauma, recent studies have shown that primary colonic anastomosis is safe even though mechanical bowel preparation is not performed before surgery. 10,11 These data therefore may bring into question the utility of mechanical bowel preparation in elective colon and rectal surgery. The aim of this study was to assess whether elective colon and rectal surgery may be safely performed without preoperative mechanical bowel preparation.