An ulcer is an open sore in the lining of the stomach or intestine. Peptic ulcers are eventually caused by acid and pepsin, a digestive stomach enzyme. These ulcers can occur in the stomach, where they are called gastric ulcers, or they can occur in the first portion of the intestine. These are called duodenal ulcers. Peptic ulcer is a term used to describe either or both of these two types of ulcers. H. pylori and certain drugs are the two major factors that cause ulcers. This issue provides a comprehensive overview of the causes, diagnosis, and treatments of peptic ulcers, including conditions like Zollinger -Ellison syndrome. Articles are devoted to NSAID ulcers and how to prevent them, stress ulcers, and antiplatelet therapy.