Four proton pump inhibitors (PPIs) are currently marketed in various parts of the world, and all of these (lansoprazole, omeprazole, pantoprazole, and rabeprazole) are available for prescription use in the United States. As a therapeutic group, the PPIs are highly useful for the relief of symptoms and healing of gastroesophageal reflux disease, gastric and duodenal ulcer disease, eradication of Helicobacter pylori infection, prevention and treatment of nonsteroidal anti-inflammatory drug (NSAID)-associated damage, management of hypersecretory states such as Zollinger-Ellison syndrome, and care of patients with non-variceal upper gastrointestinal bleeding, or non-ulcer dyspepsia. The pathophysiologic basis of these management benefits lies in the potent gastric acid inhibitory effects of the PPIs. There are differences between the PPIs in their pharmacokinetics, pharmacodynamics, influence by food and antacids, clinical efficacy, and potential for drug interactions. It is not always clear whether these often subtle variations are necessarily of clinical importance. The physician's choice of one PPI over another must rest with her/his interpretation of the clinical importance of the generally small differences between PPIs, their approval for treatment of specific clinical indications within the physician's practice jurisdiction, and the strength of the evidence based on the quantity and quality of the supporting clinical trials.