Background: Bowel preparation is an important part of computed tomographic colonography (CTC); we evaluated two small-volume preparations for screening CTC with regard to quality of preparation and patient acceptability. Methods: Asymptomatic subjects at average risk for colorectal cancer from a community-based CTC screening program were randomized to bowel preparation comprising magnesium/bisacodyl/picolax or polyethylene glycol (PEG)/picolax. CTC images were evaluated by a blinded investigator for residual feces and fluid; subjects completed a questionnaire regarding acceptability of the preparation. Results: In 176 subjects randomized to magnesium/bisacodyl/picolax (n = 82) or PEG/picolax (n = 94), the former preparation was discontinued because of syncope or presyncope in four (5%) subjects. Another 137 subjects received PEG/picolax without a significant adverse event. There were no other major differences in acceptability of the preparations as reported by subjects. The quality of bowel preparations for reporting CTC was similar. Conclusion: For subjects having screening CTC, both small volume bowel preparations are generally well tolerated and result in minimal fluid and fecal residue; however, the magnesium/ bisacodyl/picolax preparation was accompanied by an unacceptable incidence of syncope and is no longer used by us. Background: Bowel preparation is an important part of computed tomographic colonography (CTC); we evaluated two small-volume preparations for screening CTC with regard to quality of preparation and patient acceptability. Methods: Asymptomatic subjects at average risk for colorectal cancer from a community- based CTC screening program were randomized to bowel preparation comprising magnesium / bisacodyl / picolax or polyethylene glycol (PEG) / picolax. CTC images were evaluated by a blinded investigator for residual feces and fluid; subjects completed a questionnaire regarding acceptability of the preparation. The former preparation was discontinued because of syncope or presyncope in four (5%) subjects. Another 137 subjects received PEG / picolax (n = 82) or PEG / picolax without a significant adverse event. There were no other major differences in acceptability of the preparations as reported by subjects. The quality of Bowel preparations for reporting CTC were similar. Conclusion: For CAC, both small volume bowel preparations were generally well tolerated and result in minimal fluid and fecal residue; however, the magnesium / bisacodyl / picolax preparation was accompanied by an unacceptable incidence of syncope and is no longer used by us.