Abstract: Clinical and hemodynamic studies were carried out with the purpose of evaluating the effects of enalapril in the treatment of chronic heart failure. Enalapril 10—20 mg was given once a day to 10 patients with moderate to severe congestive heart failure（coronary 6,hypertensive heart disease 2 and idiopathic congestive cardiomyopathy.）. Hemodynamic studies were done on the first day after drug administration,the same daily dose was maitained for 2 weeks. The results showed a 18.29% decrease in mean BP（p＜0.01）,40.4% in CVP,23.9% in mPAP,41.2% in PCWP,39.9% and 41.3% in SVR and PVR respectively（P＜0.001）.Cardiac index increased 44.16%（P＜0.001）.The theraputic action maintained and lasted for more than 24 hours by one dose.No further drop of BP 2 weeks later.Six patients primarily in NYHA class Ⅲ and 2 in Class Ⅳ improved to class Ⅱ.No severe side effects were found. The results showed that enalapril was well tolerated in single dose as well as in 2 weeks continous therapy,showing both hemodynamic and subjective sympton improvement.