The ECGs of 157 patients were registered continuously during the oesophago-gastro-duodenoscopy with a R-R intervall monitoring system. The behavior of frequencies and cardiac arrhythms of 53 patients with and 104 patients without heart diseases is reported. 32 patients were premedicated with 0,5 mg Atropin intravenously, 121 patients received intramuscular premedication. The influence of the vegetative nervous system is discussed in view of the heart actions during the diagnostic procedure. A clinically relevant danger for the heart and circulatory system caused by oesophago-gastro-duodenoscopy was not observed.