The effect of simultaneous administration of control-released HGF on the efficacy of CM Tx in a rat myocardial infarction (MI) model was investigated. HGF-impregnated gelatin hydrogel sheets, which enable HGF to be released in situ over 2 weeks was developed. MI was created by ligating the left coronary artery in Lewis rats. The rats that developed moderate-sized MI were divided into GroupI, II and III. Transplanted CMs were found over the whole MI area in Group I, while few donor CMs were detected in the center of the scar in Group II. The result shows that simultaneous application of HGF-impregnated gelatin hydrogel sheets may enhance the efficacy of CM Tx by improving the survival rate of donor CMs in chronic MI.