Mechanical cleansing of the colon prior to elective colorectal surgery is a dogmatically established belief in surgery. Polyethylene glycol was extensively used in the 1980's and 1990's but has been largely replaced by other laxative solutions such as sodium phosphate which are better tolerated by the patient. Evidence-based data in the surgical literature question the dogma of routine mechanical bowel cleansing (8 randomized controlled studies and 4 meta-analyses). These data show with a good level of evidence that mechanical bowel preparation is unnecessary and perhaps harmful.