The effect of 120 mL (4 oz) of scotch whiskey (40% alcohol) on nocturnal gastroesophageal reflux was studied by ambulatory esophageal pH monitoring. Seventeen healthy volunteers were studied on two occasions, using a computerized radiotelemetric esophageal pH monitoring system. The subjects were given the alcohol during the second session, three hours after the evening meal, and went to bed at their usual time. Seven of the 17 subjects had prolonged supine reflux episodes on the night of alcohol ingestion. These lasted an average of 47.1 minutes (23.2 to 91.8 minutes) and occurred on an average of 31/2 hours after ingestion of whiskey and 1.4 hours after lying down. None of the subjects had these episodes on the control night. There was also a significant acidic shift in the cumulative percentage of data points below a pH of 3 and a pH of 4 in the supine position on the night of alcohol ingestion compared with the control night. This study has shown that there was a significant exposure of the distal esophagus to acid and that the normal acid clearance of the esophagus in the supine position was impaired after only moderate amounts of alcohol.