PURPOSE: Assessment of the gastroesophageal reflux disease (GERD) influence on myocardial ischemia and autonomic nervous system (ANS) activity. MATERIAL AND METHODS: In 50 patients with angiographically confirmed ischemic heart disease (IHD) in I-III CCS class, simultaneous 24-hour ECG and esophageal pH-metry monitoring was performed. We assessed: (1) GERD occurrence in patients with IHD, (2) influence of pathological reflux (PR) on myocardial ischemia--number and total duration of ST depression episodes in GERD and non-GERD patients, (3) temporary activity of ANS was determined according to the dynamics of spectral HRV (Heart Rate Variability) analysis components (LF, HF, VLF, LF/HF). RESULTS: 23 patients (46%) fullfilled the GERD criteria. Patients with GERD had significantly higher number of ST depression episodes (4.13 vs 2.85, p = 0.013) as well as longer total duration of ischemia (64.73 vs 35.2 min, p = 0.034). Spectral HRV analysis showed the significant decrease of LF/HF ratio (p < 0.035), which indicates the sympathovagal balance shift towards the parasympathetic system caused by PR. CONCLUSIONS: 1. GERD is frequent condition in patients with angiographically confirmed IHD. Coexistence of GERD may predispose to the myocardial ischemia. 2. Gastroesophageal reflux may cause the shift of sympathovagal balance towards its parasympathetic component. This mechanism may induce esophago-cardiac reflex, leading to diminished myocardial perfusion.