Cardiac fibrosis is a pathological feature common to numerous forms of heart disease, including myocardial infarction; ischemic, dilated, and hypertrophic cardiomyopathies; and heart failure. The cellular basis of fibrosis is the adverse accumulation of collagens and other ECM proteins, which impairs ventricular function and predisposes the heart to arrhythmias. The purposes of this study are to clarify the adverse effects of diabetes mellitus and hypertension on cardiac manifestations as well as to focus on the characteristic features of cardiac remodeling induced by diabetes and hypertension particularly cardiac fibrosis to address the molecular mechanism underlying them.