Helicobacter pylori, which is responsible for the most common infection worldwide, has been implicated in several gastrointestinal diseases, such as peptic ulcer disease, gastric adenocarcinoma, and mucosa-associated lymphoid tissue (MALT) lymphoma. In this article, Dr Knigge discusses the unique adaptation of H pylori to the acidic gastric environment and describes diagnostic tests to identify the organism, treatment recommendations, and tools to confirm eradication of infection.