Background. Population Helicobacter pylori screening and treatment has been advocated as a means of reducing mortality from gastric cancer. The optimum Helicobacter pylori eradication therapy to use in this setting is uncertain.Aims. To compare efficacy of seven days of omeprazole, clarithromycin and either metronidazole, or amoxycillin in Helicobacter pylori positive subjects detected by population screening.Patients. Helicobacter pylori positive patients from the placebo group of a population screening and treatment trial were invited to take part in the investigation.Methods. Patients were randomised to receive either omeprazole, clarithromycin and metronidazole or omeprazole, clarithromycin and amoxycillin, and Helicobacter pylori eradication was verified with a 1 3 C-urea breath test at least four weeks after completion of therapy.Results. A total of 221 patients took part in the study and 210 completed the protocol. Treatment was successful in 93111 (84%) patients allocated to omeprazole, clarithromycin and metronidazole and in 96110 (87%) allocated to omeprazole, clarithromycin and amoxycillin in an intention-to-treat analysis (p=0.46). Per protocol eradication rates were 93107 (87%) in the metronidazole, and 96103 (93%) amoxycillin group (p=0.129).Conclusions. There was no significant difference between the two regimens. The eradication rates achieved are comparable with previous studies in both dyspepsia and peptic ulcer patients.