The aim of the study was to assess the relationship between changes in heart rate variability (HRV) and parameters of neuroendocrine activation in patients with various levels of left ventricular dysfunction. Measurements of HRV, plasma norepinephrine (PNE), and plasma atrial natriuretic peptide (ANP) were performed in 17 age- and gender-matched control subjects (group C) and in 39 patients with ischemic heart disease or cardiomyopathy who were subdivided into 3 equal groups according to their left ventricular ejection fraction: group N (normal); group M (mildly impaired); and group S (severely impaired). Spectral analysis of HRV (from 10-min electrocardiograms) was analyzed by the method of coarse-graining spectral analysis. PNE and ANP were significantly elevated in group S only (p<0.05). Log low-frequency power and log total power for group M were significantly lower than for group N (p<0.05). Log high-frequency power was significantly lower for group M than for group C (p<0.05). Thus, assessment of changes in HRV, which were observed earlier in the progress of left ventricular dysfunction than changes in neuroendocrine factors, may be a useful non-invasive method for the early detection of autonomic abnormality in patients with left ventricular dysfunction.