Plasma levels of the tumoral carbohydrate 125 antigen marker (CA 125) have been found elevated in patients with heart failure. We measured the plasma levels of CA 125 and other tumoral markers in a group of patients with chronic heart failure and we found a correlation between the serum levels with some left ventricular parameters calculated with transthoracic echocardiography (ETT). We studied 200 patients, 159 males and 41 females, suffering from idiopathic or ischemic cardiomyopathy, 126 of them in NYHA class II, 39 in class III, and 35 in NYHA class IV. CA 125 levels were correlated with Doppler mitral flow E-wave, E/A ratio, deceleration time (DT), isovolumetric relaxation time (IVRT), and myocardial performance index (MPI) (r = 0.38, 0.35, -0.46, -0.48, and 0.35, respectively, all with P < 0.05). Multiple regression analysis found the following parameters to be independently correlated to CA 125: long- and short-axis diameter, MPI, IVRT, and E/A. Plasma CA 125 levels were raised in patients with chronic heart failure and were related to clinical condition and to diastolic and systolic function parameters of the left ventricle. CA 125 could be used as an additional, noninvasive, easily determinable, and low-cost marker of the clinical condition of patients affected by heart failure.