Background: Currently available aqueous purgatives used before colonoscopy are poorly tolerated. We designed a tableted sodium phosphate purge that we believe will yield much greater patient acceptance. Methods: A total of 305 outpatients undergoing routine diagnostic colonoscopy were randomized to one of three preparation groups: Colyte (100 patients), Fleet Phospho-Soda (106 patients), or sodium phosphate tablets (99 patients). Endoscopists were blinded to the type of preparation administered and answered a questionnaire regarding preparation quality. Patients answered a questionnaire designed to analyze tolerability. Adverse events were closely followed and recorded. Results: There were no significant differences in quality of preparation across the groups (80% excellent or good, 4% repreparation). Although hypocalcemia (4 of 71), hypokalemia (18 of 68), and hyperphosphatemia (39 of 69) were observed in patients receiving the tablets, no adverse events occurred. Patients preferred taking the tablets over Colyte and Fleet Phospho-Soda. Conclusion: The evaluation of a novel delivery system of a sodium phosphate purge is described. Intended for use before colonoscopy, it circumvents the poor taste and excessive volume of ingestion that are aversive to patients. The tableted purgative is equally effective, safe, and greatly preferred over the existing aqueous preparations. This may improve patient compliance with recommendations for screening colonoscopy. (Gastrointest Endosc 2000;52:346–52.)