Although Helicobacter pylori is both a frequent cause of gastritis and an important factor in duodenal ulcer recurrence, no treatment regimen exists that is completely safe and effective. We have studied a short eradication regimen of tripotassium dicitrato bismuthate 120 mg four times daily and amoxycillin 500 mg four times daily for seven days with metronidazole 400 mg five times daily for three days (days 5-7). 106 patients with peptic ulceration and non-ulcer dyspepsia, who were also infected with H pylori, were entered into the study. H pylori was successfully eradicated in 76/106 (72%) patients (median follow-up 9.3 months). The rate of eradication was higher among patients with metronidazole-sensitive H pylori (40/43, 93%). In 17/30 patients in whom eradication failed, pretreatment metronidazole-resistant strains were subsequently isolated. Side-effects were mild, the commonest (24/106, 24%) being taste disturbance with metronidazole. A one-week eradication regimen is a safe, effective, cheap, and well-tolerated treatment for metronidazole-sensitive H pylori.