Helicobacter pylori is associated with diffuse superficial gastritis and is one of the dominant causal factors for duodenal ulcer disease. More recent knowledge has revealed that apart from NSAID-related ulcers, H. pylori is also highly associated with gastric ulcer disease. Follow-up of duodenal ulcer patients has revealed that the prevalence of duodenal ulcer relapse was sharply diminished after successful cure of H. pylori infection. The few data available concerning relapse rates of gastric ulcer disease indicate a striking reduction of recurrence of gastric ulceration after successful eradication of H. pylori. One of the most intriguing questions is why only a small percentage of H. pylori-infected patients develop peptic ulcer disease. The most recent literature is discussed concerning subtypes of H. pylori and virulence factors, making one H. pylori strain more pathogenic compared to the other. In addition, literature is discussed concerning the question whether gastric and duodenal ulcer disease are two different entities, or whether they are at opposite sites of one disease spectrum. Finally, the most current anti-H. pylori-treatment modalities are summarized.