The exercise ECG's and coronary arteriograms of 158 patients were examined to evaluate the relationship of exercise-induced axis shifts and S-T-segment elevations to coronary artery disease. Eighteen of the 158 patients had exercise-induced S-T-segment elevations. Seventeen of these 18 patients had severe obstruction of the major coronary artery most compatible with the zone of ischemic localization. This obstruction was greater than 85 per cent in 16 patients and greater than 50 per cent in a seventeenth patient. The remaining patient had a normal coronary arteriogram and the most minimal exercise-induced S-T-segment elevations. Nine of the 158 patients had exercise-induced right axis shifts. Only 4 of these 9 patients had greater than 50 per cent obstruction of a major coronary artery, as compared to 103 of 154 patients in the total group studied. Also, there was no trend toward predominant involvement of any particular coronary artery in these 4 patients. Hence, it appears that this finding is not predictably associated with severe localized coronary artery disease. Only 4 of the 158 patients had exercise-induced left axis shifts. Three of these four patients had complete obstruction of the left anterior descending artery. But the group size was small, and the fourth patient had a normal coronary arteriogram. Hence, it is only possible to suggest that this finding may be associated with severe disease of the left anterior descending artery. The results of coronary artery surgery are discussed in a patient who had both a left axis shift and precordial S-T-segment elevations on his preoperative exercise ECG.