The effects of nitroglycerin ointment (15 mg nitroglycerin) on hemodynamics at rest and during exercise were studied in 12 patients with coronary artery disease and exertional angina (angina group) and in 8 patients with normal coronary arteriograms or with nonsignificant arteriographic abnormalities who did not have exertional chest pain (nonangina group). In both groups at rest nitroglycerin ointment induced within 15 minutes a significant decrease in left ventricular end-diastolic pressure that was sustained for at least 60 minutes; systemic arterial pressure also decreased within 15 minutes and continued to decrease during the 60 minutes of observation. By 30 to 60 minutes there were significant decreases in cardiac index, stroke index, left ventricular stroke work index and tension-time index. During exercise performed 60 minutes after receiving nitroglycerin ointment, 10 of the 12 patients in the angina group had no pain, whereas 2 had delayed and less severe symptoms. Hemodynamic observations during this exercise period revealed significant decreases in left ventricular end-diastolic pressure, systemic pressure and tension-time index from values in the initial exercise period; heart rate remained unchanged. These data document the protective effect of nitroglycerin ointment for a period of at least 60 minutes and also suggest that the beneficial effects are related to a reduction in myocardial oxygen requirements.