Recognition of the value of objective parameters in the diagnostic evaluation for coronary arterial occlusive disease had led to increased application of maximal-stress multiple-lead electrocardiography. Changes in the ST-segment during and immediately following exercise are the most significant electrocardiographic indicators of myocardial ischemia. When such causes of ischemia as congenital anomalies, embolism, and arteritis have been excluded, exercise testing is a sensitive and specific means of detecting coronary arterial occlusion. The sensitivity and specificity of this parameter are evaluated in terms of long-term morbidity and mortality and, more recently, through correlation of electrocardiographic results with angiographic evidence. In our series of 308 patients undergoing both exercise testing and coronary arteriography, the sensitivity factor for 80 negative stress tests approached 95 per cent, with only four false-negative resting and exercise electrocardiograms. For 129 patients with ST-segment changes indicative of myocardial ischemia, angiography demonstrated significant coronary stenosis in 84 per cent of the cases. Of the twenty patients with false-positive stress electrocardiograms twelve were females, wich correlates with the generally higher rate of false-negative stress-electrocardiographic response among women.