&NA;For the past decade peroral, orthograde, polyethylene glycol‐electrolyte lavage solutions (PEG‐ELS) have been the preferred bowel‐cleansing regimens before diagnostic and therapeutic procedures on the colon and rectum. The large volume and unpalatibility of these solutions may lead to troubling side effects and poor patient compliance.PURPOSE:This study was undertaken to determine which of various colon‐cleansing methods before colonoscopy would provide greater patient acceptance while maintaining similar or improved effectiveness and safety.METHODS:Three hundred twenty‐nine patients undergoing elective ambulatory colonoscopy were prospectively randomized to one of three bowel preparation regimens. Group 1 received 41 of PEG‐ELS (n=124). Group 2, in addition to PEG‐ELS, received oral metoclopramide (n=99). Group 3 received oral sodium phosphate (n=106). All groups were evenly matched according to age and sex.RESULTS:Ninety‐one percent of all patients completed the preparation received. Sixteen percent of patients suffered significant sleep loss with a bowel preparation. When comparing the three groups, there was no difference in the assessment of nausea, vomiting, abdominal cramps, anal irritation, or quality of the preparation. Compared with other preparations, oral sodium phosphate was better tolerated. More patients completed the preparation(P≤0.001). Fewer patients complained of abdominal fullness(P≤0.001). More patients were willing to repeat their preparation(P≤0.02). Also, sodium phosphate was found to be four times less expensive than either of the PEG‐ELS preparations.CONCLUSION:All regimens were found to be equally effective. Abdominal symptoms and bowel preparation were not influenced by the addition of metoclopramide. The oral sodium phosphate preparation was less expensive, better tolerated, and more likely to be completed than either of the other preparations.