We tested possibility of the use of apelin-12 as a biomarker of chronic heart failure (CHF). The study comprised 108 patients with I-IV functional class CHF of various etiology (ischemic heart disease, dilation cardiomyopathy) and 40 healthy volunteers. Blood samples were taken at hospital admission before prescription of pharmacological therapy. In all patients we carried out echocardiography with calculation of end-diastolic and end-systolic volumes (EDV, ESV) and ejection fraction (EF). Blood plasma apelin-12 concentration was compared with CHF market NT-proBNP. Mean apelin-12 concentrations were 0.86+/-0.22 hg/ml in healthy volunteers and 0.8+/-0.35, 0.81+/-0.29, 0.68+/-0.38, 0.82+/-0.35 hg/ml in patients with CHF classes I, II, III, IV, respectively. There was no significant differences between appelin-12 concentrations in various classes of CHF. No correlations were found between apelin-12 and EF, EDV, ESV, sex, age, smoking, body mass index, and NT-proBNP level. Concentration of NT pro-BNP level correlated with CHF severity. Thus apelin-12 did not show itself as reliable biomarker of CHF.