A high prevalence of left ventricular dysfunction in insulin-dependent (type-I) diabetics has been reported. However, the exact influence of metabolic control and/or the coexistence of early diabetic microangiopathy is unknown. Thus, we assessed left ventricular function by echophonocardiography in 50 type-I diabetics (mean age 26 ± 7.9 years), who showed a fairly good metabolic long-term control (mean hemoglobin Al: 8.8%) after the introduction to intensified insulin therapy in comparison with 50 age- and sex-matched controls. Type-I diabetics did not differ from controls in their left ventricular internal diameters, mean wall thickness, ratio of pre-ejection period to left ventricular ejection time and systolic shortening fraction. Isovolumetric relaxation period reflecting an early diastolic event was slightly but significantly prolonged in diabetic subjects, independent of metabolic control status or existence of early microangiopathy. Isovolumetric relaxation period showed a statistically significant correlation to age in type-I diabetics, but not in controls. Possibly, the diabetic status – although well-controlled, but not normalized – may biochemically alter the myocardium and might influence its diastolic properties.