Congestive heart failure (CHF) may be caused by systolic dysfunction (SD) of the left ventricle (LV) or isolated diastolic dysfunction (DD). Differentiation between SD and DD is important because each one requires a different form of therapy. In order to evaluate if some clinical and/or echocardiographic differences exist between patients(pts) with CHF from SD or DD we have analysed a group of 120 pts admitted to our Division with severe CHF (NYHA III-IV). After clinical evaluation all pts underwent a complete Echo-Doppler examination at the time of admission. SD was considered present if LV end-diastolic diameter (LVEDD) greater-than-or-equal-to 56 mm and LV fractional shortening (FS %) < 25%. DD was considered present if LVEDD and FS were both within a normal range. Furthermore, wall thickness and LV filling by Doppler Transmitral flow during early filling (Evel) and atrial contraction (Avel) were measured. Results: CHF was caused by SD in 90 pts (75%) and by DD in 30 pts (25%), p < 0.001. SD was due to dilated cardiomyopathy (83 pts), ischemic or idiopathic, and to severe aortic stenosis (7 pts); DD was due to aortic stenosis (20 pts), hypertrophic cardiomyopathy (4 pts) and hypertensive cardiopathy (6 pts).