Sleep-related gastroesophageal reflux and esophageal acid clearance have been shown to be important components in the pathogenesis of reflux esophageal disease. Previous studies have suggested that patients with more severe esophagitis are distinguished by an accumulation of acid mucosal contact time during sleep. These data would suggest that patients with Barrett's esophagus should have particularly severe impairment of acid clearance, most notable during sleep. To address this issue, 16 asymptomatic healthy volunteers and 13 patients with Barrett's esophagus were studied. Acid clearance was assessed by timing the reestablishment of an esophageal pH of 4 following the infusion of 15 ml 0.1 N HCl. Sleep was polygraphically monitored in order to objectively determine sleep and waking. The results indicated that while patients with Barrett's esophagus had a marked increase in the frequency of spontaneous gastroesophageal reflux during sleep, they unexpectedly demonstrated faster acid clearance times during both waking and sleep. A greater percentage of arousal responses to acid infusion during sleep was noted in the Barrett's group. It is concluded from these results that patients with Barrett's esophagus can adequately clear acid from the distal esophagus but experience considerable acid mucosal contact through repeated episodes of spontaneous reflux during sleep.