Abstract: AIM: To explore the protective effects of captopril and benazepril on reversal of myocardial interstitium remodeling. METHODS: Sixty male Sprague Dawley rats were randomly divided into normal group (n=15) and streptozotocin (STZ)-induced diabetic group (n=45). Diabetic rats were randomly subdivided into diabetic control group, captopril-treated group and benazepril-treated group (15 rats in each group). Captopril or benazepril was administered each day at concentrations of 50 mg/kg and 10 mg/kg, respectively. After 9 weeks, all rats were sacrificed. SP immunohistochemical staining was used to detect the level of type I collagen, type III collagen and the expression rate of Fas/FasL protein. Transmission electron microscope was used to observe the changes of cardiocytes and collagen. RESULTS: Compared with the normal group, cardiac index, expression rate of Fas protein and level of type I and type III collagen in the diabetic group all significantly increased (P<0.05), whereas no difference was observed in the expression rate of FasL protein. Compared with the diabetic control group, indexes were all improved in the two treated groups, but the cardiac index and collagen in captopril-treated group was less effective than in the benazepril-treated group. CONCLUSION: Interstitial remodeling occurs in diabetic cardiomyopathy. Despite some slight differences, both captopril and benazepril improve heart function by reducing the expression of types I and III collagen and decreasing the expression rate of Fas protein.