Objective To evaluate the myocardial protection of warm blood cardioplegic induction during cardiopulmonary bypass(CPB) Methods Twenty-eight adult patients undergoing valve replacement ,were devided randomly into two groups : in group test (group T,n=14) the warm (35℃-37℃) blood cardioplegia was infused to induce ECG straight line ,followed by the administration of the cold (6℃-8℃) blood cardioplegia , whereas in group control (group C ,n=14) the cold blood cardioplegia was applied simply The aterial blood samples were taken to measure the plasma concentration of cardiac troponin T (cTnT) with ELISA methods immediately after anesthesia induction,and immediately ,6 h, 24 h after the weaning from CPB The myocardial samples of right atrium were taken to observe the morphology with the transmission electron microscpe Results The rate of restoring spontaneous heart-beat in group T (93%) was significantly higher than that in group C (50%) One case in gruop T (7%) and three cases in group C (21%) required the interim pacemakers No case in group T (0%) and five cases (36%) in group C required the administration of dopamine perioperatively The durations of post-operative mechanical ventilative support and ICU-staying of group T were obviously shorter than those of group C The plasma level of cTnT in group T was obviously lower than that in group C immediately and 6 h after CPB Myocardial morphology in group T got much better outcome than that in group C did Conclusions Warm blood cardioplegic induction during CPB can provide better myocardial protection than cold blood cardioplegic induction