Autonomic neuropathy, particularly cardiovascular autonomic neuropathy (CAN) is one of the complications of the diabetes mellitus both types. It leads to life comfort\'s declination but may also be the direct cause of death in diabetes mellitus patients. It seems that degree of metabolic control and duration of the disease is connected with prevalence and severity of CAN. The aim of our study was to assess cardiac autonomic function in young subjects suffered from insulin-dependent diabetes mellitus (IDDM) with relatively short duration time of the disease. We subdivided 25 (m-12, f-13) IDDM patients aged from 18 to 30 years: mean--26 +/- 38 years, with duration time of the disease up to 10 years, normotensive and without nephropathy and retinopathy. We created 25 healthy volunteers control group with similar age and sex. In all selected subjects full Ewing\'s battery tests were performed as well as the spectral analysis of power heart rate variability (HRV) was assessed with Finapress device (Ohmeda 2300) and automatically computed with special software. HRV in total spectrum power TP from 0.001-0.5 Hz, high frequency (HF) band from 0.15-0.3 Hz, low frequency (LF) band from 0.03-0.15 Hz and LF/HF ratio were examined both in supine and tilt. All assessed spectral values were significantly lower in IDDM patients then these in controls whereas LF/HF were respectively higher. Valsalva tests and deep breathing HR response tests were significantly differed among groups but within normal limits. We concluded that when spectral analyse was performed, in young IDDM patients with short duration time of the disease, impairment of cardiac autonomic function was observed.