To assess the influence of a therapeutic dose of 0.5 mg sublingual nitroglycerin (NTG) on left ventricular performance, 32 patients with coronary heart disease were studied. After routine coronary angiography the patients underwent cinearteriography and phonomechanocardiography before and four minutes after NTG administration. After NTG, end-diastolic pressure and systolic aortic pressure fell significantly, while heart rate, ejection fraction and dp/dt increased. After NTG, a significant prolongation of the pre-ejection period index (PEPI) and isovolumetric relaxation time (IVRT), increase in the PEP/LVET ratio and decrease of the "a" wave of the apexcardiogram were found. The usual therapeutic sublingual NTG dose causes profound haemodynamic changes which are due to decreased preload and afterload and altered contractility induced by NTG.