Time and frequency domain analysis of heart rate variability is generally accepted method for the investigation of the activity of the autonomic nervous system in terms of control of cardiovascular functions. Many studies showed that deacreased heart rate variability is related to higher risk of mortality in patients with myocardial infarction, in diabetic subjects, and with increased mortality in the general population. Besides the prognostic importance of heart rate variability in patient who already are diagnosed with cardiovascular disorder, there are many observations, that some autonomic imbalance and changes in components of heart rate variability may preceed clinical symptoms of diseases of cardiovascular system. The relation of the decreased total heart rate variability with incidence of coronary heart disease, myocardial infartion or heart failure has been reported. The studies on offspring of hypertensives showed impaired function of the autonomic nervous system even before development of hypertension. The prospective observations, with several years long follow-up, showed an important role of the frequency domain components of heart rate variability in prediction of the incidence of hypertension. Heart rate variability, as the method allowing assessement of the autonomic nervous function seems to be promising for the stratification of the risk of incidence of cardiovascular disorders or mortality. However, there is no agrrement, which parameters should be used for risk stratification and the consensus on normal values has not yet been reached.