INTRODUCTION: Intrauterine growth restriction (IUGR) has been associated with an increased risk of cardiovascular disease in later life. The regularity mechanism of cardiovascular system is under the control of autonomic nervous system (ANS). The non-optimal fetal growth may alter the development of the ANS and this appears to persist in later life. The aim of the present work is to analyse the synergic activity of the ANS in normal and growth restricted children. MATERIAL AND METHODS: Heart rate variability analysis from 24 h ECG recordings of 70 children between 9 and 10 years old, normal and IUGR was performed using linear and non-linear time series analysis techniques. CONCLUSION: The HRV parameters showed no significant difference between normal and IUGR children. Low birth weight and its association with development of the cardiovascular system and its control have been extensively studied. In order to investigate the effect of low birth weight on HRV parameters, the IUGR children were further divided into two groups: IUGR-1 (birth weight<2.50 kg) and IUGR-2 (birth weight>/=2.50 kg). The results demonstrated that most of the HRV measures showed significant differences between normal versus IUGR-1 as well as IUGR-1 versus IUGR-2 groups. The effect of gender on HRV measures was also examined and we noticed that girls had lower HRV than boys.