Autism spectrum disorder (ASD) is a serious neurodevelopmental disorder, associated with autonomic dysregulation. However, the pathomechanism leading to autonomic abnormalities is still unclear. The aim of this study was to assess autonomic nervous system (ANS) activity during baseline in homogenous group of autistic children using electrodermal activity (EDA), as an index of sympathetic activity and short-term heart rate variability (HRV) reflecting predominantly cardiac vagal control. Fifteen ASD boys and 15 healthy age-matched boys at the age of 7-15 years were examined. The continuous EDA and ECG were recorded during resting phase in a supine position. Evaluated parameters: EDA amplitude (microS), RR interval, spectral power, peak frequency and power spectral density in low (LF-HRV: 0.04-0.15 Hz) and high-frequency (HF-HRV: 0.15-0.4 Hz) bands of HRV spectral analysis. In ASD group we found significantly shortened RR intervals (729+/-20 ms vs. 843+/-30 ms, p=0.005), lower mean EDA (0.66+/-0.13 microS vs. 1.66+/-0.42 microS, p=0.033), reduced spectral activity and power spectral density in HF-HRV compared to controls (2.93+/-0.12 ms(2) vs. 3.38+/-0.10 ms(2), p=0.01; 4.12+/-0.10 ms(2)/Hz vs. 4.56+/-0.11 ms(2)/Hz, p=0.008, respectively). We suggest that impairment in resting autonomic regulation associated with ASD could represent an important pathomechanism leading to potential cardiovascular complications in ASD.