Tosifen was synthesized originally in a series of compounds whose basic structural moiety, the sulfonyl urea nucleus, was of interest for potential hypoglycemic action. But tosifen is only a weak hypoglycemic agent. It is a potential antianginal and antiarrhythmic agent. The duration of action of tosifen was considerably longer than nitroglycerin and its lack of side effects considerably greater than propranolol. No long-term harmful effects have been observed during 13-week toxicity studies in animals. Tosifen differed from standard antianginal agents which may act via beta-adrenergic blocking activity or alteration of cardiac or circulatory dynamics since no acute pharmacological changes were observed after tosifen was administered. Tosifen was readily absorbed in both rats and dogs. The rates of absorption, metabolism, and urinary excretion were higher in the rat than in the dog.