Background: In chronic obstructive pulmonary disease (COPD) patients, functional and structural changes of the respiratory system greatly influence cardiovascular autonomic functions. Determining autonomic balance may be important in understanding the pathophysiology of COPD and useful clinically in the treatment of COPD patients. Heart rate variability (HRV) and heart rate turbulence (HRT) are useful tools in assessing the autonomic neurovegetative function. Our aim in this study was to evaluate the HRV and HRT variables in COPD patients. Twenty five moderate to severe COPD patients and 25 healthy subjects were included in this study.