To study the effects of acute mental stress on gastric and pancreatic secretion, 12 healthy fasting volunteers swallowed two multilumen tubes, which allowed continuous aspiration of gastric and duodenal juices and measurement of motility of the stomach and the duodenum. In each study at least three duodenal phase III complexes of the migrating motor complex were recorded. In randomized order after the first or second duodenal phase III, mental stress was induced for 60 min by means of solving anagrams and doing mental arithmetic. Mental stress significantly increased the duration of the migrating motor complex by 60% (137.9 +/- 16.3 vs 86.1 +/- 13.0). Gastric flow rate and gastric acid output were not significantly altered. Duodenal flow rate was not changed during the stress period but significantly decreased by more than 52% in the following 30-min resting period. Duodenal concentration and output of chymotrypsin were significantly increased during the second 30-min period of acute mental stress; chymotrypsin output was significantly reduced in the poststress period. We conclude that acute mental stress has different effects on the stomach, the pancreas, and the upper gastrointestinal motility. The mechanisms by which the central nervous activity induced by mental stress affects the motility and secretion of the upper gastrointestinal tract remain to be elucidated.