Glyceryl trinitrate (GNT, 0.8 mg) was administered in a spray to 15 coronary patients of whom 7 had a pulmonary wedge pressure (PWP) greater than 16 mm Hg on exercise (subgroup I) and the others (subgroup II) had a normal PWP at rest and during exercise. At rest, GNT increased heart rate and decreased cardiac output, systolic index, stroke work index, right atrial pressure, pulmonary wedge and mean systemic pressures in all patients. Peripheral resistances did not change. During exercise, GNT lowered PWP, systemic arterial pressure and peripheral resistances in all cases. It increased cardiac output as well as systolic and stroke work indices only in patients of subgroup I. In subjects with coronary disease, no overt cardiac failure but elevated PWP on exercise, GNT in a spray can quickly improve exercise capacity and hemodynamic reserves and increase anginal threshold.