Left ventricular heart function was investigated by means of two dimensional (2D) echocardiography and pulsed Doppler (PD) echocardiography in 17 young consecutive patients aged 17-38 years (mean 26.6 y.) with type I diabetes mellitus of short duration (mean 5.5 y.) whose stress ECG showed no signs of ischemic heart disease and who had no other organic complications of diabetes. The series was compared with 13 healthy volunteers (mean age 25.5 y.). No differences were found between diabetics and controls in systolic function parameters (left ventricular fractional shortening, interventricular septum shortening, left ventricular posterior wall shortening, left ventricular endsystolic dimension) as established by 2D. The parameters of left ventricular diastolic filling (maximal velocity of the rapid filling period E, its maximal time and duration of the whole phase) were established by PD and computer assisted approach. These parameters were studied also during atrial systole A and the E/A ratio was determined. All findings were comparable in the group of diabetics and controls, with the only statistically significant difference (p less than 0.05) in the duration of A which was shortened in the diabetics.