Helicobacter pylori and Zollinger-Ellison syndrome. Helicobacter pylori (previously Campylobacter pylori) is almost invariably associated with chronic duodenal ulcer disease. The relationship between H. pylori infection and duodenal ulcer in Zollinger-Ellison syndrome is unknown. We investigated the frequency of H. pylori infection in Zollinger-Ellison syndrome and also what effect H. pylori infection had on gastric function in patients with Zollinger-Ellison syndrome. H. pylori infection was diagnosed based on a specific serologic (ELISA) assay based on high-molecular-weight cell-associated proteins of H. pylori. We studied 20 patients with Zollinger-Ellison syndrome; 15 men and 5 women ranging in age from 24 to 71 years, median age 51. Six Zollinger-Ellison syndrome patients had H. pylori infection compared to 100 consecutive patients with chronic recurrent duodenal ulcer disease (P less than 0.05). Pretreatment basal acid output in Zollinger-Ellison syndrome patients ranged from 7.9 to 95.0 mmol/hr, median 35.2. Pentagastrin-stimulated maximal acid output ranged from 8.5 to 132 mmol/hr; median 52.7. Acid secretion was lower in the H. pylori-infected patients than the uninfected patients (BAO 24.5 +/- 6.5 vs 45.4 +/- 6.6, and MAO 44.3 +/- 11.8 vs 67.9 +/- 10.7, for H. pylori infected vs uninfected patients, respectively). The difference in BAO was statistically significant (P less than 0.05). The present results indicate that H. pylori is not a major contributing factor in duodenal ulcer associated with Zollinger-Ellison syndrome. The association of a reduced BAO with H. pylori suggests that these findings may be related. 