Heart rate turbulence (HRT) is a chronotropic response of the sinus heart rhythm to ventricular premature beat (VPB). Children show decreasing heart rate together with the maturation of the autonomic nervous system. The aim of the research was to assess the relationship between HRT parameters, age, and heart rate and time domain heart rate variability (HRV) parameters in healthy children. Twenty-four-hour ECG Holter recording was performed on 398 healthy children. The mean RR interval preceding VPB, number of VPBs, and HRT parameters-turbulence onset (TO) and turbulence slope (TS)-were determined. We observed significant correlation among TS and mean RR and age. Children with prepubertal status have lower values of TS compared with those during puberty. According to given quartiles, upper for TO was Ն-0.8%, lower for TS was Յ4.56 ms/RR, 13 patients (3%) obtained abnormal both TO and TS. The correlations between HRT and HRV parameters were observed among the youngest children. Age and heart rate preceding VPB have no effect on HRT onset in children, whereas HRT slope is highly dependent on these variables. Our results support hypothesis that in older children HRT is dependent on autonomic tone and also determined by other intrinsic modulators. T he term "heart rate turbulence" (HRT) was first used by Schmidt et al. (1) and refers to changes in the sinus heart rhythm after ventricular premature beat (VPB). The response consists of a short phase of early heart rate acceleration followed by heart rate deceleration. HRT can be quantified by two parameters, turbulence onset (TO) and turbulence slope (TS), which are strong and independent markers of a sudden cardiac death risk in various patients' cohorts (1,2). The underlying mechanism of described parameters is connected with compensatory activation of baroreceptor reflex triggered by a decreased stroke volume following a VPB. The HRT response is believed to be under strong dependence on parasympathetic activity and heart rate preceding VPB (3). Recent studies have shown that HRT phenomenon can be used as an alternative measure of baroreflex sensitivity (4,5).A few studies demonstrate that in healthy subjects increasing age is associated with a decrease of HRT slope (6,7), likewise an increase in heart rate is relevant to TO decrease. However, there is a lack of information about heart rate turbulence behavior after VPB and the potential influence of age and pubertal status on healthy subjects within first two decades of life. Changes in basic heart rhythm during child's development are influenced by breathing frequency, sleeping periods and maturation of sympathetic and parasympathetic systems (8). We hypothesized that in such population age heart rhythm may significantly influence the heart rate turbulence parameters.The aim of this study was to determine the correlation among the HRT parameters, age, heart rate, heart rate variability (HRV) parameters and pubertal status in healthy children. MATERIALSAll the participants had a documented history of vent...