Hypertension is a major worldwide health problem. Its prevalence is 1.5-2 times higher in diabetic population than that in non-diabetic individuals. Its pathogenesis depends on diabetic nephropathy in type 1, whereas may be multifactorial in type 2 diabetes mellitus. In diabetics, angiotensin converting enzyme inhibitors are most widely preferred in the treatment of hypertension because of their numerous desirable effects. In this article, the most recent data are presented on the relationship between diabetes mellitus and hypertension, and on the epidemiology, pathogenesis, and treatments of hypertension in diabetic patients.