Nonulcer dyspepsia with or without duodenitis and duodenal ulcer disease are often considered to be a spectrum of the same acid-peptic process. Some reports evaluating basal gastric acid secretion in nonulcer dyspepsia and duodenal ulcer disease have supported that impression; however, results from different studies have been mixed. In order to compare basal gastric secretory profiles in nonulcer dyspepsia and duodenal ulcer disease, we determined basal acid outputs in 66 consecutive patients with the diagnosis of nonulcer dyspepsia. All patients with nonulcer dyspepsia had at least a three-month history of epigastric abdominal pain, and all had negative upper gastrointestinal endoscopies except for 14 with duodenitis. The 66 patients with nonulcer dyspepsia were compared to 40 asymptomatic normal subjects and 114 patients with endoscopically documented duodenal ulcer disease. There was no significant difference in mean basal acid output among all 66 patients with nonulcer dyspepsia (2.9 +/- 2.7 meq/hr), the group of normal subjects (3.2 +/- 2.7 meq/hr), the 14 patients with nonulcer dyspepsia with duodenitis (3.0 +/- 2.1 meq/hr), and the 52 patients with nonulcer dyspepsia without duodenitis (2.9 +/- 2.9 meq/hr). However, mean basal acid output of the patients with duodenal ulcer disease (9.1 +/- 7.6 meq/hr) was significantly higher than all the other groups (P less than 0.001). The gastric acid secretory profiles determined in this study do not appear to support the view that nonulcer dyspepsia with or without duodenitis and duodenal ulcer disease are a spectrum of the same acid-peptide process.