During cardiac catheterization, isosorbite dinitrate (ISDN) was given intravenously to ten patients with confirmed left ventricular failure (10 NOMC, 1 ischemic cardiopathy, 1 valvular disease). When the left ventricular filling pressure was above 15 mmHg and the systemic systolic pressure exceeded 100 mmHg, a 500 gamma (first half of patients) or 800 gamma (second half of patients) bolus of ISDN was given intravenously, followed by an infusion of 2.5, 5 or 10 mg ISDN per hour. In all patients, the functional tolerance was excellent ; the heart rate remained unchanged and the systolic systemic pressure decreased only slightly (10 %). Left ventricular filling pressures returned to normal in four patients, decreased significantly in three, and remained unchanged in three. The cardiac output increased significantly in four patients. The poor initial hemodynamic conditions and the doses given, subsequently considered insufficient especially during the first part of the study, probably explain why ISDN was only partly effective.