The aim of the present study was to determine the relationship between the variability in systolic blood pressure and pulse intervals with respect to baroreflex sensitivity in two age groups of children. A causal interrelationship between SBP and PI variability, and BRS was independent of age, but it was age-dependent for BRSf. This difference could be explaind by the significant prolongation of mean PI with age, because BRS is dependent on mean PI.