Chronic congestive heart failure (CHF) is a complex clinical syndrome characterized by marked neurohormonal activation which may lead to further decompensation of the circulatory system. This study was undertaken to establish the role of certain hormones in pathogenesis of congestive heart failure. Plasma levels of brain natriuretic peptide (BNP), cyclic 3'5'-guanosine monophosphate (c-GMP), endothelin 1 (ET-1), and noradrenaline (NA) were examined in patients in patients with CHF and with decompensation of circulatory system. The survey was made in 92 patients with CHF, among them there were 42 females aged 50-76 years (mean 66 years) and 50 males aged 53-76 years (mean 68 years). All patients were divided into 3 groups according to NYHA classification. On admission blood samples were taken from all patients to determine plasma levels of BNP, c-GMP, ET-1, and NA. Then patients received captopril and furosemide. Next blood samples were taken between 5 and 7 day of the treatment, after entire remission symptoms of decompensation. Plasma levels of BNP, c-GMP, ET-1, and NA were estimated with radioimmunoassay. Our study showed that plasma levels of ET-1, BNP, c-GMP, and NA were increased in patients with CHF. 5-7 days of the treatment with ACE inhibitor and diuretic caused significant decrease of ET-1, BNP, and c-GMP levels, but did not influence NA plasma levels. Determination of ET-1, BNP, c-GMP, and NA plasma levels may be a noninvasive method useful in estimation of degree of CHF and efficacy of the treatment.