Sodium salicylate consistently produces a prompt increase in heart contractile force when injected in anesthetized dogs in doses of 100 mg./Kg. intravenously. The increase in force is about 30 per cent and declines to control levels in 15 to 20 min. This effect is not considered of important therapeutic significance. Total doses of about 400 mg./Kg. consistently produce marked hyperpyrexia which closely resembles that of dinitrophenol and applied external heat in its circulatory characteristics; conspicuous features are extreme tachycardia, depressed S-T segment, moderate increase in heart force, and aortic pulse contours which indicate reduced stroke volume and vasodilation.