We analyzed the acute, direct effects of nitroglycerin (NTG) tape on the coronary arteries and hemodynamics in 38 patients who underwent coronary angiography. The diameters of the 3 main coronary arteries were compared among the angiograms obtained at baseline, 15 minutes following transdermal administration of 10 mg (8 patients) or 25 mg (30 patients) of NTG (Millisrol tape), and after intracoronary injection of 2.5 mg isosorbide dinitrate (ISDN). Only the left main trunk and proximal portion of the left anterior descending artery dilated after 10 mg of transdermal NTG administration (p < 0.05). However, every measured coronary segment (segments 1-8, 11, and 13) dilated (p < 0.05) after 25 mg of NTG. Systemic blood pressure decreased slightly but significantly from 150 +/- 22 to 147 +/- 21 mmHg during the study, with no change in heart rate. Left ventricular end-diastolic pressure decreased significantly from 16 +/- 7 to 14 +/- 5 mmHg. We conclude that 25 mg of transdermal NTG tape dilates coronary arteries and is applicable for acute coronary syndrome, with few complications.