Abstract: Objective: The purpose of the present study is to investigate the protective effects of HOE 642 （cariporide） on immature rabbit heart Methods: Twenty four New Zealand rabbits （2to3 weeks old） were randomly divided into two groups （n=12,each group） Isolated working rabbit heart model was subjected to this study The hearts were perfused in a Langendorff apparatus and submitted to 60.minutes of normothermic ischemia with cardioplegia per 20.minutes and 25minutes of reperfusion Group I received St Thomas Hospital cardioplegic solution No2 as cardioprotective solution Group II received the same cardioplegic solution as group I with addition of cariporide （10μmol/l） The left ventricular function was recorded,which included left ventricular systolic pressure （LVSP）,left ventricular diastolic pressure （LVDP）,coronary artery flow（CAF）,mean aortic pressure（MAP）,aortic flow （AF） and dp/dt max The levels ofcreatine phosphokinase （CK）,lactic dehydrogenase （LDH） of coronary sinus venous solution were measured Results: Before myocardial ischemia,there were no significant differences in all above mentioned parameters in two groups But after reperfusion thepercentage of recovery of myocardial function in group II was much better than group I,the LVDP-LVSP-MAP-AF-CAF and dp/dt max showed markedly better recovery in group II The release of CK,LDH was significantly increased in group I （P＜0.001） Conclusions: Hoe 642（cariporide） with St Thomas Hospital No 2 solution can provide much better myocardial function recovery for immature myocardium in ischemia/reperfusion than St Thomas hospital No 2 solution only