SummaryAlthough the currently most eVective treatment regimens cure about 90% of infections, 10% of patients remain Helicobacter pylori positive. Several factors contribute to treatment failure. These include patient compliance, bacterial resistance to antibiotics, and treatment related issues. Treatment failure leads to the development of bacterial resistance to metronidazole and clarithromycin. Retreatment can be undertaken after considering several diVerent strategies: to repeat the same regimen with full doses of medications and a longer treatment duration, or to choose diVerent regimens to avoid the antibiotic previously used, or to switch to proton pump inhibitor (PPI) based quadruple therapy or ranitidine bismuth citrate (RBC) based triple therapy. In principle, full doses and longer treatment durations are advisable. As retreatment is always diYcult, choosing the best available first line treatment regimen is still the best "rescue" treatment.

Although the incidence of gastric cancer has declined dramatically in Western countries, the most recent data from the International Agency for Research on Cancer show that it remains the second most common cancer worldwide and caused 628 000 deaths in 1990. The incidence and prevalence of gastric cancer are projected to increase over the next few decades in less developed countries as a result of the increased longevity of H. pylori-infected populations and improved therapies. Gastric carcinogenesis is a multistep and multifactorial process beginning with H. pylori-associated gastritis in most cases. H. pylori infection, together with other environmental factors and individual susceptibility, determine the ®nal risk for the development of gastric cancer. The magnitude of H. pylori infection as a risk factor for gastric cancer in the published H. pylori and