Abstract： Objective To investigate the effect of rat hemeoxygenase-1 (rHO-1) gene carried by recombinant adeno-assoeiated virus (rAAV) on myocardial isehemia/reperfusion (I/R) injury in rats. Methods Ninety-five healthy male Sprague-Dawley (SD) rats weighing 225～250 g were randomly divided into four groups: sham operation group (Ⅰ, n=8); normal saline group (Ⅱ , n=29); rAAV-EGFP (enhan ced green fluorescent protein)group (Ⅱ, n=29)and rAAV-rHO-1 group (Ⅳ, n=29). In Ⅱ ,III and Ⅳgroups,600μl of normal saline,rAAV-EGFP or rAAV-rHO-1 was injected intramyocardially at four sites onthe anterior and posterior walls of left ventricle. After 3 months, 3 animals in each group were sacrificed. EGFP-expression in heart sections was observed under fluorescence microscope. The expression of HO-1 in the injected myocardium was detected by immunohistoehemistry and reverse transcription-polymerase chain reaction (RT-PCR). The remaining animals in the four groups were anesthetized, traeheostomized and mechanically ventilated. I/R of myocardium was producing by blocking the left anterior descending branch of coronary artery (LAD) for 30 minutes followed by 120 minutes reperfusion. After the successful reproduction of the model, the animals were killed and their hearts were harvested for determination of myocardial infarct size, apoptotic index (AI), and pathology changes in myocardial tissue. Results The expression of EGFP was detected in group Ⅲ only, and transfeetion efficiency was (53.5±2.0)%. AI was significantly higher in groupⅡ, group Ⅲ and group Ⅳ than in group I (all P<0. 01). The expression of HO-1 mRNA and protein was significantly higher, and the infarct size and AI, were significantly lower in group Ⅳ than in group Ⅱ and group Ⅲ (all P<0. 01). The degree of damage to myocardial tissue was significantly severer in group Ⅱ and group Ⅲ than in group Ⅰ and group Ⅳ. There was no significant dift'erenee between group Ⅱand group Ⅲ. Conclusion rAAV-mediated rHO-1 gene transfeetion may attenuate myocardium I/R injury by inhibiting apoptosis of cardiomyocyte in rats.