Thirty-three dyspeptic patients with colonization of Helicobacter pylori in the gastric antrum were treated with tripotassium dicitrate bismuthate 120 mg q.d.s. for 28 days and metronidazole 250 mg q.d.s. for 10 days starting on day 19. Five weeks after cessation of this treatment regimen H. pylori was eradicated in 23 patients. In 8 of the remaining 10 patients, H. pylori had become resistant to metronidazole. In this study resistance was significantly associated with smoking habits, but not with age, bacterial load, gastritis score or alcohol consumption.