BACKGROUND: Impairment in cardiovascular autonomic regulation participates in the onset and maintenance of primary hypertension. OBJECTIVE: The aim of the present study was to evaluate cardiac autonomic control using long-term heart rate variability (HRV) analysis in adolescents with primary hypertension. SUBJECTS AND METHODS: Twenty two adolescent patients with primary hypertension (5 girls/17 boys) aged 14-19 years and 22 healthy subjects matched for age and gender were enrolled. Two periods from 24-hour ECG recording were evaluated by HRV analysis: awake state and sleep. HRV analysis included spectral power in low frequency band (LF), in high frequency band (HF), and LF/HF ratio. - RESULTS: In awake state, adolescents with primary hypertension had lower HF and higher LF and LF/HF ratio. During sleep, HF was lower and LF/HF ratio was higher in patients with primary hypertension. CONCLUSIONS: A combination of sympathetic predominance and reduced vagal activity might represent a potential link between psychosocial factors and primary hypertension, associated with increased cardiovascular morbidity.