Is therapy with digitalis indispensable, or can patients in frank congestive heart failure be successfully treated by mercurial diuresis alone? There has been no adequate documentation of the hemodynamic effects of diuretics given to the point of loss of all edema in these patients. Rader and associates1 have recently described the results of such a clinical experiment, as well as a comparison of the cardiovascular effects produced by subsequent administration of digitalis. Repeated administration of a noncardiac-acting diuretic (mercaptomerin [Thiomerin] sodium) to 14 patients with congestive heart failure resulted in relief of signs and symptoms of circulatory congestion in all patients and improvement in cardiodynamic function in one half of these subjects. Diuresis did not change intrinsic myocardial function in the other half of the patients; subsequent digitalis therapy in these individuals produced increased cardiac output and a decrease in the arteriovenous oxygen difference toward normal values.