In 15 patients with mild, chronic congestive heart failure the effect of a single dose of captopril (25 mg/m2 b.s.) on heart rate, systolic and diastolic blood pressure as well as on left ventricular function was studied at rest and after a submaximal physical effort. Preejection period (PEP), left ventricular ejection time (LVET) and the contractility index PEP/LVET were polycardiographically determined++. Left ventricular end diastolic volume (DVol), and systolic volume (SVol), ejection fraction (EF), stroke volume index (SVI) and cardiac index (CI) were estimated using two-dimensional echocardiography. Obtained data indicate, that in patients with chronic, congestive heart failure, a single dose of captopril lowers blood pressure at rest without significant changes of hemodynamic parameters, but improves left ventricular function during physical effort.