Serum levels endothelin-1,2 aldosterone, renin activity were performed in 52 patients with chronic congestive heart failure during captopril therapy. The investigations were done before therapy, after 10-15 days therapy and after disappearance symptoms of heart failure. The levels endotelin-1,2,aldosterone and renin activity were determined using radioimmunologic methods. Fraction ejection and peripheral vascular resistance were determined by echocardiography technics. It was found that serum endothelin levels in patients with chronic congestive heart failure were increased proportionally to functional class of heart failure and decreased after disappearance symptoms of heart failure. An increase in plasma endothelin concentration has not correlated with ejection fraction, aldosterone concentration and renin activity. These studies have demonstrated that in patients with congestive heart failure on captopril therapy endothelin serum levels positively correlates with peripheral vascular resistance. No correlation was found between ejection fraction and activity renin-angiotensin-aldosterone system. These findings indicated that captopril therapy decreases endothelin production.