In various clinical types of heart ischemic disease (stenocardia of stress and rest, large scale- and small scale myocardial infarction) alterations in activity of glycolysis and Krebs cycle enzymes as measured in leukocytes were especially distinct under conditions of large scale myocardial infarction as compared with the small scale infarction and stenocardia. Energy metabolism of leukocytes in heart ischemic disease was altered due to functional impairment of these cells, of the cellular immunity state as well as to the alteration in the activity of hydrolytic enzymes of leukocytes accumulating in the inflammatory infiltrate in myocardium. In the ischemic disease of heart the gas transport functions of erythrocytes were altered; the cells, exhibiting high resistance and elevated activity of the pentose-phosphate shunt, were found in circulation. The metabolic alterations in erythrocytes affected the rheological properties of blood. Estimation of enzymatic activity in blood cells is important for diagnosis of the heart ischemic disease of various types.