Beyond peptic ulcer disease, Helicobacter pylori infection is associated with intestinal-type gastric cancer and low-grade gastric mucosa-associated lymphoid tissue (MALT) lymphoma. It is also currently implicated as a possible cause of dyspepsia and extraintestinal disorders such as coronary artery disease, rosacea, chronic urticaria, and delayed growth in children. There are strong epidemiological data from large cohort studies linking H. pylori to gastric adenocarcinoma. Several cofactors, including early childhood acquisition of infection, strain-specific differences, genetic predisposition of the host, and the environment, appear to play a role in the progression of chronic gastritis to gastric cancer. H. pylori infection is seen in over 90% of MALT lymphomas, and about 70% of localized nonbulky tumors will undergo complete histological regression after eradication of the bacterium. Because follow-up data are limited to less than 2 years, those undergoing H. pylori eradication as primary therapy for MALT lymphoma require frequent histological surveillance for tumor recurrence. There are conflicting data from short-term studies regarding the effect of H. pylori eradication on dyspeptic symptoms. The decision to test or not for H. pylori in the dyspeptic patient may become easier when well-controlled studies with longer periods of follow-up become available. Because H. pylori induces a systemic inflammatory response, investigators are beginning to explore possible extraintestinal disease associations with the infection. The global prevalence of both peptic ulcer disease and gastric cancer has led to studies focusing on noninvasive screening for H. pylori in high-risk populations and prevention of primary infection by means of vaccination.