Chlorbenzoxamine is an antimuscarinic agent used for the treatment of peptic ulcer disease and other functional gastrointestinal disorders. Chlorbenzoxamine, a structural analog of hydroxyzine, produces a unique antagonism of gastric ulceration induced in rats and dogs by various procedures. This effect is not accompanied by a significant gastric secretory depression or a reduction in gastric acid concentration. Chlorbenzoxamine does not show anticholinergic or antihistaminic activity in vitro but does produce a nonspecific depression of isolated smooth muscle. The antiulcer effect of chlorbenzoxamine in rats is abolished by hypophysectomy suggesting a central or endocrine mechanism of action.