Abstract: Myocardial myoglobin was studied immunohi stochemically in 12 dogs by ligation of left anterior descending coronary artery.The results showed a definite myoglobin loss from ischemic area follow-ing coronary occlusion for 60 min and 90 min. By comparison of immunoperoxidase staining with concomitant study of light microscope, depleties of myoglobin indicating myocardial ischemic lesion was demonstrated, while ischemic but not necrotic fibers stained relatively normally with eosin-hematoxylin. These findings suggested that immu-noperoxidase staining of myocardial myoglobin be used to detect early myocardial ischemic lesion.