An exaggerated increase in meal-stimulated gastrin is a common finding in patients with duodenal ulcer. Duodenal ulcer patients also exhibit an increase in the number of parietal cells, which results in an increase in maximum acid output. There are also data to suggest that acid hypersecretion may not predate the ulcer disease, but is acquired, possibly due to the trophic effects of the exaggerated gastrin release on parietal cells. We investigated meal-stimulated gastrin release in nine Helicobacter pylori-infected individuals; eight patients with chronic duodenal ulcer and one H. pylori-infected healthy control, both before and after therapy designed to eradicate H. pylori infection. We also simultaneously measured intragastric pH in six duodenal ulcer patients. Eradication of the H. pylori infection reversed the exaggerated meal-stimulated gastrin release (gastrin secretion fell from 141 + 16 pg/ml/h before treatment to 98 +/- 7 pg/ml/h after, p less than 0.01) without affecting intragastric pH. Whereas exaggerated meal-stimulated gastrin release may be an important pathogenetic feature of duodenal ulcer disease, we conclude that it is secondary to the H. pylori infection. This study provides further insight into the role of H. pylori in the pathogenesis of duodenal ulcer disease. We postulate that reversal of the abnormalities in gastrin secretion will be associated with a gradual return of gastric secretion to normal.