We study 71 type I diabetics and 25 controls, trying to analyze the anatomical and functional changes due to diabetes. The diabetics, with a mean age of 18.4 +/- 8.2 years, were strictly selected excluding any disease and treatment besides insulin. In 66, and echocardiographic M mode and 2D study was done to calculate wall thickness, cavity dimensions and systolic function indexes; in all, Eco-Doppler analyzing 9 diastolic function indexes. The results showed an increase in septal thickness in diabetics (p less than 0.01 in diastole and less than 0.001 in systole). There was no difference in systolic function or posterior wall thickness, having the diabetics a significant increase of the T 1/2 (p less than 0.001), a decrease of the deceleration of E and the ratio E/A (p less than 0.001). As a group, 12.5% of the diabetics had anatomical abnormalities, and 18.3% diastolic abnormalities at least in two indexes. The only significant correlation was established between the evolution time and the T 1/2 (p less than 0.01). We conclude that in this group of selected diabetics, the anatomical and functional abnormalities found were only imputable to the diabetic abnormality.