H. pylori has been found in high percentages of patients with various gastric conditions. It plays a key role in the pathogenesis of peptic ulcers by breaking down the mucosal defense barrier and stimulating an inflammatory response. Peptic ulcers are caused by an imbalance between aggressive factors like acid and pepsin and defensive factors in the stomach and duodenum. Common causes include H. pylori infection, stress, smoking, NSAIDs, and genetic factors. Symptoms include epigastric pain, vomiting, hematemesis, and weight loss. Endoscopy and biopsy are important for diagnosis. Chronic ulcers can lead to complications if large and deep.