100 consecutive patients with both duodenal ulcer and Campylobacter pylori infection were followed up to see whether eradication of C pylori affected ulcer healing or relapse. Patients were randomly assigned to 8 weeks of treatment with cimetidine or colloidal bismuth subcitrate (CBS), with tinidazole or placebo being given concurrently from days 1 to 10, inclusive. Endoscopy, biopsy, and culture were done at entry, in weeks 10, 22, 34, and 62, and whenever symptoms recurred. There was no maintenance therapy. C pylori persisted in all of the cimetidine-treated patients and in 95% of those treated with cimetidine/tinidazole, but was eradicated in 27% of the CBS/placebo group and 70% of the CBS/tinidazole group. When C pylori persisted, 61% of duodenal ulcers healed and 84% relapsed. When C pylori was cleared 92% of ulcers healed (p less than 0.001) and only 21% relapsed during the 12 month follow-up period (p less than 0.0001).