PURPOSE: This study was undertaken to determine whether a mechanical bowel preparation with 90 ml of sodium phosphate (NaP) solution (Group II) increased the acceptability of bowel preparation and reduced discomfort compared with 2 liters of polyethylene glycol (PEG) combined with a bisacodyl 20 mg (Group I). METHODS: We conducted a prospective, randomized, single-blinded study. Forty-four patients undergoing elective colorectal surgery in the National Health Insurance Corporation Ilsan Hospital from March 2002 to November 2002 were included in this study. We assessed the patients' tolerance and cleansing ability, as well as the surgeon's satisfaction, by using a structured questionnaire. Postoperative complications were also evaluated. RESULTS: Patient tolerance to NaP was higher than it was to PEG (P=0.034). The cleansing ability and the surgeon's satisfaction were not different between the two groups (P=0.217, P=0.349). There is no significant postoperative complication except for 1 case of wound infection in both group. CONCLUSIONS: Both oral solutions proved to be equally effective and safe. However, patient tolerance to the small volume of NaP demonstrated a clear advantage over the traditional PEG solution.