Obesity is associated with autonomic nervous system dysfunction. The aim of the study was to evaluate baroreflex sensitivity, an indicator of autonomic nervous function, in 20 obese children and adolescents in comparison with 20 age- and sex-matched nonobese subjects. All subjects were examined in the supine position over a period of 50 min. Systolic blood pressure (SBP) and RR intervals were monitored continuously. Baroreflex sensitivity was assessed by cross-spectral analysis of SBP and RR interval oscillations (BRS index) and SBP and heart rate oscillations (BRSf index) within the low frequency range (0.04-0.15 Hz). Sensitivity was determined in 3 time intervals of 3 min each to evaluate changes during rest. The BRS index was significantly lower in obese children and adolescents than in the nonobese control group (p = 0.002). Significant changes in the BRS index over time (p = 0.004) were found only in nonobese subjects. In contrast, the BRSf index increased over time in both groups (p = 0.01), and no significant between-group difference was detected. In conclusion, obese children and adolescents show decreased resting baroreflex sensitivity with less variation compared with nonobese subjects. The BRS and BRSf indices appear to be only partially correlated.