Objectives : Essential hyperhidrosis is a socially and occupationally disabling disorder. There are many suggestions that hyperhidrosis is associated with the autonomic nervous system, especiallythe sympathetic system. This study was designed to investigate the autonomic nerve system in patients with essential hyperhidrosis and healthy controls by the frequency domain analysis of heart rate variability (HRV). Methods : 17 head-hyperhidrosis patients in the ambulatory care were investigated. All were inspected at the first medical examination. using the PSA of HRV. HRV was measured for minutes after 5 minutes bed rest. We checked the frequency domain analysis of HRV (i.e. TP, VLF, LF, HF) which were transformed into natural logarithm of patients against the standard measures of the HRV components. Then we compared the values of patients with means of normal Korean subjects. Results : The values of natural logarithmic measure of HRV (LnTP, LnHF, LnLF, LnVLF) of patients With head-hyperhidrosis we examined were $6.85{pm}1.61$, $4.93{pm}$2.00, $5.40{pm}1.83$, and $6.13{pm}1.37$, respectively. None of these values were higher than means of normal subjects. Conclusions : This study suggests that the function of the autonomic nervous system does not increase in patients with head-hyperhidrosis.