Experiments on dogs with acute coronary insufficiency were made to show that nonachlazine in doses of 3 and 5 mg/kg considerably reduces or even prevents the rise of S-T segment on the epicardial electrogram depending on the intensity of ischemia. Hydroxyfedrine in doses of 0.1 and 0.3 mg/kg deteriorates the electrogram. Nonachlazine prevents an increase in the content of lactate and in the lactate/pyruvate ratio in the blood outflowing from the focus of ischemia. On the contrary, hydroxyfedrine raises the characteristics in question. Nonachlazine improves blood supply of the ischemized myocardium, increases the retrograde coronary blood flow and redistributes blood in favour of the affected myocardial area. Hydroxyfedrine lowers the retrograde blood supply of the area of ischemia and redistributes blood in favour of the unaffected areas of the heart.