Diconium bromide, 2-(3,4-dichloroanilino)-quinolizinium bromide, a potent antispasmodic in the lower bowel of the dog, was found in the present study to exert gastric acid-antisecretory and antiulcerogenic activities in the rat stomach. These effects were demonstrated by means of short- and long-term pyloric ligation, acetylsalicylic acid (ASA)-induced ulcerogenesis, and cold-and-restraint stress studies. A reduction of gastric acid concentration by the drug was probably responsible for the decrease in the degree of ulceration and hemorrhagic lesion formation. The drug's inhibition of stress hemorrhagic lesions may be related to an effect both on gastric HCl secretion and on the vasculature in the glabdular mucosa. The delay of gastric emptying by diclonium bromide results from its known antispasmodic or smooth-muscle depressant action. The toxicity of diclonium bromide, perorally, was low in rats and overt signs of drug effect were not evident until toxic doses were administered. It is concluded that diclonium bromide may represent a useful non-anticholinergic drug effective in treating both peptic ulcers and spasticity of the colon (irritable-colon syndrome) in man.