This study compares the effects and duration of the effects of 5 mg. of sublingual (SL) isosorbide dinitrate (ISD), 20 mg. of oral ISD, and 0.4 mg. of SL nitroglycerin (TNG) on central circulatory dynamics. Twenty-seven patients with coronary artery disease were evaluated with radioisotope techniques and determinations made of heart rate (HR), blood pressure (BP), cardiac index (CI), stroke volume index (SVI), left ventricular enddiastolic volume index (LVEDVI), and left ventricular ejection fraction (LVEF). There were significant and equivalent reductions in BP, SVI, LVEDVI, and CI 15 minutes after TNG, 1 hour after SL ISD, and 4 hours after oral ISD in addition to comparative increases in HR and EF by all drugs at these same time intervals. The effects of TNG were gone at 30 minutes while changes in LVEDVI, LVEF, and CI were present 4 hours after SL ISD and persistent changes in LVEDVI and SVI present 6 hours after oral ISD. We conclude that nitrates have significant effects on both preload and afterload and that the duration of effects of sublingual and oral ISD are truly long acting as compared to TNG.