Objective. To present normal spontaneous baroreflex sensitivity (BRS) values and investigate the influence of posture, sex, age, pubertal stage, body mass index (BMI), and physical activity level on BRS in (pre)adolescents. BRS is a sensitive measure of both sympathetic and parasympathetic cardiovascular regulation that may help detect early subclinical autonomic dysfunction. Design. A cross-sectional cohort study in a large sample of 10-13-year-old Dutch (pre)adolescents from the general population. Methods. Short-term spontaneous BRS was determined non-invasively by Portapres in both the supine and standing position. BRS was calculated by power spectral analysis using the discrete Fourier method (frequency band 0.07-0.14 Hz). Univariate statistical methods and multiple regression analyses were applied. Results. BRS in a standing position was lower than in a supine position (9.0 +/- 4.9 versus 15.3 +/- 9.1 ms/mmHg; t = 27.8, P < 0.001). Girls had lower BRS values than boys in both postures (supine 14.3 +/- 8.7 versus 16.4 +/- 9.4 ms/mmHg, [beta] = 0.12, P < 0.001; standing 8.4 +/- 4.4 versus 9.5 +/- 5.4 ms/mmHg, [beta] = 0.08, P = 0.012), independent of age, pubertal stage, BMI, and physical activity. Lower limits (P2.5) for normal BRS values in supine and standing positions were for girls 3.6 and 2.2 ms/mmHg and for boys 3.9 and 2.5 ms/mmHg, respectively. BRS declined with age in the standing position ([beta] = -0.13, P < 0.001). In obese (pre)adolescents, BMI was negatively associated with BRS during standing (Kendall's [tau] = -0.26, P = 0.010). Conclusion. The BRS of (pre)adolescents was negatively related to female sex, age, and obesity. A reduced BRS in obese (pre)adolescents might be a candidate predictor of future cardiovascular health, and therefore warrants further exploration.