Seven of 45 patients with Barrett's esophagus prospectively followed with yearly endoscopy had histological evidence of squamous mucosa overlying Barrett's epithelium. This histological finding has previously been identified as a rare sequela of anti-reflux surgery. All seven patients had specialized columnar epithelium. No evidence of the overlying mucosa was recognized at endoscopy. Only one patient had previous anti-reflux surgery. During the observation interval, three patients had a decrease, and four had no change in the length of Barrett's epithelium. Squamous mucosa overlying columnar epithelium in Barrett's esophagus is not infrequent, and prior anti-reflux surgery is not a necessary precondition.