BACKGROUND High Helicobacter pylori eradication rates have consistently been reported with 2-week dual therapy regimens of ranitidine bismuth citrate plus clarithromycin. Ranitidine bismuth citrate with two antibiotics may provide an alternative 1-week eradication regimen. METHODS This double-blind, randomized, parallel group, international, multicentre study compared ranitidine bismuth citrate 400 mg b.d. and clarithromycin 500 mg b.d. for 2 weeks (RC) with ranitidine bismuth citrate 400 mg b.d., clarithromycin 500 mg b.d. and metronidazole 400 mg b.d. for 1 week (RCM) for eradication of H. pylori in 350 patients with dyspepsia. RESULTS Treatment with RC and RCM eradicated H. pylori (established by the combination of two negative results from two discrete 13C-UBTs at nominal weeks 4 and 12) from 89% (95% CI: 84-94) and 92% (95% CI: 88-97) of the observed population, and from 78% (95% CI: 72-84) and 80% (95% CI: 75-86) of the intention-to-treat population. When established only by one negative 13C-UBT result at least 28 days after the end of treatment, the respective intention-to-treat rates were 85% (95% CI: 79-90) and 88% (95% CI: 83-93). Both regimens were well-tolerated, only 6% of patients given RC and 4% given RCM discontinued treatment. Median plasma bismuth concentrations at the end of the second week of study were low, at 3.5 and 0.4 ng/ mL, respectively. CONCLUSIONS Ranitidine bismuth citrate triple therapy for 1 week (RCM) and dual therapy for 2 weeks (RC) were equally effective for the eradication of H. pylori infection.