The aim of the study was to determine the relationship between the variability in systolic blood pressure and pulse intervals with respect to the baroreflex sensitivity in borderline hypertensive children. A causal interrelationship between the0.1Hz variability of systolic blood pressure and pulse intervals and baroreflex sensitivity was shown. An unchanged pulse interval variability in borderline hypertensive children could be explained by their low BRS coupled with a primarily higher variability in systoliv blood pressure. In borderline hypertensive, an increased variability of systolic blood pressure might be an early sign of an increased sympathetic activity, and it explains a relatively high pulse intervals variability at low BRS.