Accurate evaluation of the efficacy of therapy in angina pectoris is difficult, for since cardiac pain is a subjective sensation with no constant outward manifestations, it is necessary to rely almost wholly on the patient's description of his symptoms. Variations in the physical and emotional activity of daily life, changes in the prevailing temperature and other factors difficult to evaluate cause changes in the frequency and severity of attacks of angina and make conclusions regarding therapeutic measures uncertain. In a previous communication1 it was shown that under standardized conditions a definite measurable amount of exercise will always induce a typical attack of angina in a given patient. This "standardized exercise tolerance test" has been used to measure objectively the therapeutic benefit derived from procedures such as total thyroidectomy2 and to measure the heart rate and blood pressure during attacks of angina.3 The present communication deals with its