30 patients suffering from stable angina pectoris were studied by triaxicardiometric (polarcardiographic) method. Triaxicardiometry including the X, Y, Z Frank leads, azimuth (H°), elevation (V°) angle derivations and spatial magnitude (M) tracings were taken at rest and after submaximal bicycle ergometer exercise. After receiving 30 mg/day isosorbide dinitrate for a minimum of 5 days the whole procedure was repeated, stored by an analogue tape recorder and evaluated by a TPA/i computer. It has been stated that the method of triaxicardiometry has an excess sensitivity on the demonstration of ischemic alteration of anterior and posterobasal left ventricular wall compared to the traditional X, Y, Z leads. According to the pre- and post-exercise bicycle ergometer testing estimated by triaxicardiometry, isosorbide dinitrate caused a significant reduction of subendocardial myocardial ischemia.