Since Helicobacter pylori was first isolated by Warren and Marshall in 1983, many investigators have reported that it is closely associated with gastro-duodenal diseases. Several diagnostic methods, C-urea breath tests, rapid urea test, histological exam and culture, are used for detecting H. pylori. Japanese monkey and Mongolian gerbils is the animal model that can sustain persistent colonization with H. pylori. Japanese monkeys persistently infected with H. pylori can develop histological gastritis quite similar to that in humans. Eradicating H. pylori markedly reduces the recurrence of peptic ulcers. The new triple therapy regimen consisting of proton pump inhibitor (PPI) plus two antibiotics is effective for eradicating H. pylori. This therapy has shown high rates of H. pylori eradication (90%) with few side effects. An increase in the prevalence of antibiotic-resistant H. pylori strains has been reported worldwide. Failed attempts to eradicate the bacteria resulted in an increased number of H. pylori resistant strains. The relationship between H. pylori infection and gastric cancer has been recently investigated.