A prospective study of patients with symptoms of gastroesophageal reflux was undertaken to determine the prevalence of Barrett's esophagus and reevaluate the diagnostic approach necessary to detect this complication. Endoscopy with mucosal biopsy was performed in 97 subjects. Twelve (12.4%) were found to have Barrett's esophagus. The sensitivity and specificity of the endoscopic and radiologic examinations for Barrett's esophagus were prospectively evaluated. Endoscopy (92%) was significantly more sensitive than radiology (24%) in detecting Barrett's esophagus (p less than 0.001). The frequency and severity of reflux symptoms among patients determined to have Barrett's esophagus, reflux esophagitis, or normal esophageal biopsies were quantitatively similar in all three groups, except for significantly greater daytime heartburn in those with reflux esophagitis (p less than 0.01). These data indicate that Barrett's esophagus complicates gastroesophageal reflux more often than previously believed.