GERD (Gastroesophageal Reflux Disease) is a common clinical problem, which affects the upper part of the gastrointestinal tract. The pathophysiology of GERD is associated with dysfunction of the various mechanisms called "the anti-reflux barrier". Lately, the disturbances of the autonomic nervous system (ANS) have been stressed in the pathogenesis of the different diseases (including GERD). The HRV examination (Heart Rate Variability) seems to be the best non-invasive method to evaluate the disturbances of ANS. The aim of our study was to detect possible ANS disturbances in GERD patients. 23 persons (healthy volunteers and GERD patients) took part in the examinations. 24-h-esophageal pH-metry and the resting, "deep breathing" (DB) test, as a short-term measurement of heart rate variability, were performed in every person. The results proved that the GERD patients have abnormal low values of the basic components that make up the HRV spectrum (LF and HF obtained from rest record and HF from record during DB). We demonstrated the evidence of functional ANS disturbances, which may be responsible for the changing the HRV parameters of the frequency domain analysis in GERD patients. The disturbances mentioned above are supposed to influence the normal modulation of the X (vagus) nerve, which plays an important role in the maintaining the physiological LES function.