Congestive heart failure (CHF) has been treated for several years on empiric basis, until the results of the major clinical trials have made possible a pathophysiological approach to the treatment of patients with CHF. Studies from our laboratories have demonstrated that hemodynamic and neurohormonal responses to acute volume expansion are markedly impaired in patients with dilated cardiomyopathy and mild heart failure (NYHA Class I) and that pretreatment with ACE-inhibitors is able to prevent these abnormal responses. New insights into a more pathophysiological approach to CHF treatment are now possible by the development of new noninvasive techniques for the study of cardiac function. In particular, through radionuclide techniques we were able to demonstrate that patients with CHF show an exercise induced hemodynamic response different from that of normal subjects. Both ACE-inhibitors and digitalis were able to restore a normal response to exercise in patients with CHF.