Pre-operative preparation of the colon is carried out with oral and/or intravenous administration of antibiotics and through the mechanical preparation of the colon using various substances to decrease the intraluminal bacterial concentration and remove the larger quantity of fecal material as possible, thus decreasing the risk of anastomosis dehiscence due to an increase in the intraluminal pressure. The role of antibiotics has been completely established while that of mechanical preparation is still questioned. The objective of this study is to assess the actual impact of mechanical preparation on colorectal surgery. MATERIALS AND METHODS: Forty seven patients who underwent elective colorectal surgery were prospectively evaluated, out of which only 24 had mechanical preparation. We compared variables such as age, sex, preoperative hemoglobin, albumin and leukocyte values, surgery characteristics and type of anastomosis, as well as complications in both groups. Results: We found a higher incidence of fistulas, dehiscences and general complications in the group undergoing mechanical preparation of the colon. CONCLUSION: The results show that mechanical preparation of the colon does not provide any benefit and may result in a higher incidence of complications in colorectal surgery.