Epidemiologic studies have shown that cigarette smoking is closely related to peptic ulcer disease. The mechanisms by which cigarette smoking adversely affects gastric mucosa have been suggested and elucidated. This article reviews some of the mechanisms involved in cigarette smoking-related gastric ulceration and healing. Experimental findings suggest that cigarette smoking increases xanthine oxidase activity, leukotrienes, and nitric oxide production and also neutrophil infiltration in the gastric mucosa. On the other hand, it reduces blood flow, prostaglandin production, epithelial cell proliferation, and formation of blood vessels in the tissue. These actions are important for ulcer formation and healing. The evidence thus far available strengthens the hypothesis that cigarette smoke is indeed harmful to gastric mucosa through defined mechanisms.