Helicobacter pylori (H. pylori) may be found in up to 50% of the world's population, making it the most common infectious disease worldwide. H. pylori is a gram-negative, microaerophilic rod with flagella and normally resides in the stomach. It can be diagnosed endoscopically, via breath tests, or through a simple blood test. H. pylori can usually be eradicated with a combination of proton pump inhibitors and antibiotics. Although most people infected with this organism never develop a complication, H. pylori infection in others may produce significant mucosal inflammation leading to ulcers in the stomach and duodenum. H. pylori has also been recognized as a risk factor for the development of both gastric carcinoma and mucosal-associated lymphoid tumor. Although not widely known, H. pylori can also affect organ systems outside of the gastrointestinal tract. It is now apparent that H. pylori can infect the skin, liver and heart and that these infections may produce a number of different disease states. In addition, H. pylori infection can adversely affect the nutritional status of both children and adults. This article discusses the epidemiology and bacteriology of H. pylori, reviews the different methods of diagnosing and treating this common infection, and then focuses on the effects that H. pylori has on different organ systems within the body, including the nutritional status of those affected.