This study examined cardiovascular activity and autonomic involvement during sleep in essential hypotension. We compared young female hypotensives and normotensives using ambulatory blood pressure monitoring, impedance cardiography, and frequency-domain analysis of heart rate variability during a night of polysomnographic recording. Hypotensives, as compared to normotensives, exhibited lower blood pressure, reduced myocardial contractility and reduced sympathovagal balance across the whole night. Both groups exhibited a reduction in cardiovascular involvement from wake to sleep with similar cardiovascular activity during wake and REM. No group difference was observed in sleep architecture suggesting similar sleeping quality in hypotensives and normotensives. The lower blood pressure and reduced myocardial contractility associated with a lower sympathovagal balance in hypotensives, as compared to normotensives, suggest a night-time hypoactivation of the cardiovascular system supporting the hypothesis of impairment in autonomic control in essential hypotension.