Peptic ulcers are best found on the lesser curvature side of the stomach, the gastric sinus, and the duodenal bulb. Peptic ulcers include gastric ulcers and duodenal ulcers, which are caused by the breakdown of the gastroduodenal mucosa from various etiologies, culminating in the formation of ulcers. The most common clinical causes are Helicobacter pylori infection, long-term alcohol consumption, and long-term use of nonsteroidal anti-inflammatory drugs, which clinically manifest as chronic, periodic, rhythmic epigastric pain. Gastric ulcers are predominantly painful after meals, and duodenal ulcers are predominantly hunger pains. Both gastric and duodenal ulcers can cause upper gastrointestinal bleeding, and both are at risk of perforation. Gastric ulcers and duodenal ulcers can cause bleeding in the upper gastrointestinal tract, and both are at risk of perforation.