BACKGROUND Essential hyperhidrosis (EH) is often considered to be related to an increased activity of sympathetic nervous system (SNS). However, there is a lack of studies comparing autonomic nervous system (ANS) activity in controls and in EH patients. The aim of the present study was to simultaneously investigate in patients with severe EH, blood pressure, heart rate variability and plasma catecholamine levels in comparison with controls. METHODS 19 EH patients and 20 controls with normal ANS function assessed by clinical testing were included. Blood pressure (BP) and heart rate (HR) were measured using a Finapres beat-to-beat monitor. BP and HR variabilities (Fast Fourier transformation) and plasma catecholamine levels (HPLC) were obtained at rest and during a 15 min 70 degrees head-up tilt test. RESULTS At rest, a significantly higher relative energy of low frequency band (LF) of systolic BP was observed in EH in comparison with controls contrasting with the lack of difference in BP, HR, plasma catecholamine levels and in other spectral parameters. During tilt, all changes were comparable in EH and in control subjects excepting relative energy of LF of SBP which remained unchanged when compared to the resting condition in EH group. CONCLUSIONS In EH, SNS is not over-reactive even if resting overactivity cannot be excluded.