Objective:To study the effects of N-acetylcysteine(NAC) on ischemia/ reperfusion(I/R)-induced myocyte apoptosis in diabetic rats. Methods:The I/R heart model was made by ligation of the left anterior descending coronary artery (LAD) close to its origin. The LAD was occluded for 30 min followed by removal of ligation to allow subsequent reperfusion for 3 h. 72 rats were randomly divided into two groups: non-diabetic group(C, n = 36) and diabetic group(D, n = 36). The animals in C group were randomly reassigned into sham-operated group(CS, n = 12) , I/R group(C I/R, n = 12) and treated with NAC group(CN, n = 12). The rats in D group were also reassigned to sham-operated group(DS, n = 12) , I/R group(DI/R, n = 12) and treated with NAC group(DN, n = 12). Malondialdehyde(MDA) and creatine kinase isoenzyme-MB(CK-MB) were measured. Infarct size(IS/AAR%), the apoptosis index(AI) by TUNEL staining, the number of the cells positive for Caspase-3 and positive expression index(PEI) were calculated. Results:After I/R, the IS/AAR%, CK-MB, MDA, AI and Caspase-3 PEI were higher in diabetic group than those in non-diabetic group. Treatment with NAC decreased the above parameters in both non-diabetic and diabetic rats, but the parameters in diabetic rats were higher than those in non-diabetic rats. Conclusion:Diabetic rat hearts are more susceptible to I/R-induced myocardial necrosis and myocyte apoptosis. NAC can decrease the infarct size and attenuate cardiomyocyte apoptosis in both non-diabetic and diabetic rats, but the therapeutic effects are less effective in diabetic rats than those in non-diabetic rats. Objective: To study the effects of N-acetylcysteine ​​(NAC) on ischemia / reperfusion (I / R) -induced myocyte apoptosis in diabetic rats. Methods: The I / R heart model was made by ligation of the left anterior descending coronary artery LAD) was occluded for 30 min followed by removal of ligation to allow subsequent reperfusion for 3 h. 72 rats were randomly divided into two groups: non-diabetic group (C, n = 36) and diabetic group (D, n = 36). The animals in C group were randomly reassigned into a sham-operated group (CS, n = 12), I / R group n = 12). The rats in D group were also reassigned to sham-operated group (DS, n = 12), I / R group (DI / R, n = 12) and treated with NAC group Infarct size (IS / AAR%), the apoptosis index (AI) by TUNEL staining, the number of the cells positive for Caspase-3 and positive expression index (PEI) were calculated Results: After I / R, the IS / AAR%, CK-MB, MDA, AI and Caspase-3 PEI were higher in diabetic group than those in non-diabetic group. Treatment with NAC decreased the above parameters in both non- diabetic and diabetic rats, but the parameters in diabetic rats were higher than those in non-diabetic rats. Conclusion: Diabetic rat hearts are more susceptible to I / R-induced myocardial necrosis and myocyte apoptosis. NAC can decrease the infarct size and attenuate cardiomyocyte apoptosis in both non-diabetic and diabetic rats, but the therapeutic effects are less effective in diabetic rats than those in non-diabetic rats.