AIM: To investigate the electrophysiological characteristics of ventricular myocyte both in subendocardium and in subepicardium during ischemia. METHODS: Using modified Ferrier's method of ischemic and reperfusion injury in isolated guinea pig right ventricular wall. RESULTS: The transmembranal electric activities in subendocardium and in subepicardium were all significantly abnormal, and it was more significant in subendocardium. CONCLUSION: The alteration degree of ventricular myocyte in subendocardium and in subepicardium during ischemia and early reperfusion was different, and this might be the electrophysiological basis of the vulnerability of the subendocardium.