A prolonged QT interval is considered an indicator of increased risk of malignant ventricular arrhythmias and/or sudden death. It has been proposed that autonomic neuropathy in diabetes is related to QT interval prolongation and increased mortality rates. Several studies in Type 1 and Type 2 diabetic patients have confirmed the independent relation between prolonged QT interval duration or increased QT interval dispersion and chronic ischemic heart disease. It has been consistently shown that autonomic neuropathy is related to QT interval duration while more controversies exist on the association with QT interval dispersion. In recent years, studies have confirmed the value of QT interval as a predictor of total mortality in both diabetic and non-diabetic subjects. Moreover, several studies have shown a significant relation between QT interval prolongation and cardiovascular disease risk factors. QT interval could be used to stratify the cardiovascular risk in diabetic patients. We still do not know why QT interval is prolonged and how this abnormality leads to death. Nevertheless, QT interval is a simple, low-cost measure, easily obtainable without the need of the patient's compliance and which could help to select patients who need second level diagnostic procedures and strict observation.