Hypothermia has been considered to be detrimental to myocardial protection. In order to evaluate warm blood cardioplegia effects, following CPB, 12 adult mongrel dogs were randomly allocated to be continuously perfused through aortic root with oxygenated warm blood cardioplegia (37 C) (group W, n=6)or cold blood cardioplegia (4C)(group C,n=6)indivadually. The coronary blood samples were taken before coronary perfusion(CP), 60mins and 90mins following CP,to measure the serum activities of lactate dehydrogenase (LDH),creatine phosphokinase (CPK)and glutamic-oxaloacetic transaminase (GOT)and the level of malondialdehyde (MDA). As compared with those before CP,the activities of LDH and CPK increased significantly only at 90th min following CP in group W,and at 60th and 90th min during CP in group C(P0.05) but went up markedly in group C following CP(P0.05) but rose dramatically in group C (P