Helicobacter pylori infection is a common bacterial infection for humans, and the organism is the most prevalent gastric microbial pathogen. However, the major route of transmission remains poorly understood. The outcome of chronic H pylori infection varies from asymptomatic gastritis to peptic ulceration and gastric malignancies. Recently, H pylori has been associated with the development of extradigestive disorders, including refractory iron-deficiency (sideropenic) anemia and chronic autoimmune thrombocytopenic purpura. Virulence factors of H pylori and host genetic factors are both considered important determinants of disease outcome. Multiple tests, including novel noninvasive approaches, are available for establishing the presence of H pylori infection, but there is still little consensus about which study should be performed and in what clinical setting. Eradicating H pylori uses combination therapy, including a proton pump inhibitor and 2 antibiotics taken twice daily for 7 to 14 days. Antibiotic resistance is a growing and serious problem that interferes with the success of eradication therapy. Testing and eradication therapy for H pylori are currently recommended only for the subset of infected persons in whom the disease sequelae are proven or highly suspected.