Helicobacter pylori has been identified as a major factor in duodenal ulcerogenesis. After H pylori eradication, the recurrence rate of duodenal ulcers falls dramatically and cure of this chronic relapsing disease has been claimed by several authors. H pylori eradication was first attempted with bismuth salts alone or with antibiotics. H2-receptor antagonists are not effective against H pylori, although proton pump inhibitors such as omeprazole and lansoprazole are active in vitro against H pylori. Their minimum inhibitory concentration is close to that of the imidazoles (metronidazole, tinidazole): proton pump inhibitors and imidazoles have common structural features. Consequently, lansoprazole has been tested in monotherapy and triple therapy. In monotherapy, the H pylori clearance rate with lansoprazole 30 mg during 4 weeks was 40% in our study and 19% in a study by Jhala et al. No eradication was achieved. These results were in agreement with those of another proton pump inhibitor. In triple therapy, two studies used the same regimen in nonulcer dyspepsia patients: lansoprazole 30 mg/day for 2 weeks, amoxicillin 2 g/day for 2 weeks, and tinidazole 1 g/day for 2 weeks. Pooled data from these two French trials show that H pylori eradication was achieved in 14/17 patients (82.4%). Lansoprazole administered concomitantly with two antibiotics is effective in the eradication of H pylori and is as effective as other triple therapy regimens with bismuth salts, or with other proton pump inhibitors. One of the most important problems is metronidazole resistance of H pylori strains. Antibiotics such as new macrolides (clarithromycin or roxithromycin) should be tested in a triple therapy regimen against H pylori strains with lower primary resistance.