During the clinical use of sodium dinitrophenol (1-2-4) in obese patients, the occasional appearance of subjective symptoms such as tachycardia, dyspnea and profuse diaphoresis1 suggested the necessity of investigating the effects of the drug on the circulation.Thirteen patients with apparently normal cardiovascular systems were selected for this study. Six of the group were placed at bed rest in the hospital, and control observations of blood pressure, pulse rate, vital capacity and venous pressure made regularly at 8 a. m., 2 p. m. and 7 p. m. The control period was continued until at least three consecutive results were in close agreement. A mean of three or more control results was taken as the base. The control period was never less than three days and was sometimes as long as five days. A quantity of 300 mg. of sodium dinitrophenol was then administered orally in three divided doses each day,