In 36 patients with effort angina pectoris without myocardial infarction, the sites of exercise-induced ST changes (depression and elevation) on the body surface were investigated. Exercise-induced ST depression was most often seen in left anterior chest leads. The body surface distribution of ST depression failed to identify the obstructed coronary artery. Exercise-induced myocardial ischemia was thought to extend to the greater part of the subendocardial region of the left ventricle. Exercise-induced ST elevation was mainly found on the upper right anterior chest. It has been suggested that these leads face the interior of the left ventricle and the observed ST elevation directly reflects subendocardial ischemia of the left ventricle. This data is important for evaluating ST changes in exercise electrocardiography.