Recent reports have suggested that there might be an increased risk of colonic adenomas and cancer in patients with Barrett's esophagus. We conducted a controlled prospective study investigating the risk of colonic neoplasia in 17 patients with Barrett's esophagus. Six additional patients with previous colonoscopy were considered separately. The prevalence of colonic neoplasia in these patients was compared with that in a group of 25 asymptomatic subjects participating in a screening colonoscopy study. There were three adenomas (17.6%) in the Barrett's group and 11 (44%) in the control group. Including the six Barrett's patients with previous colonoscopy, the rate was 30.4%. No cancers were found in either group. We conclude that the rate of colonic adenomas is no higher in a group of patients with Barrett's esophagus than in a group of matched asymptomatic subjects. The presence of Barrett's esophagus does not justify a special colonoscopic surveillance program.