Efficacy and safety of enalapril (5-20 mg/day) were studied in 20 patients with NYHA class II-III chronic heart failure, After 3 months of treatment NYHA,class decreased by 20,8% while physical working capacity increased by 27,7%. There was a tendency to augmentation of ejection fraction (+4%) and lowering of left ventricular myocardial mass (-5,3%). Plasma potassium and creatinine decreased by 2,9 and 8,2%, respectively. Dry cough appeared in 3 patients (15%) and required withdrawal of the drug in 2 of them (10%). The conclusion was made that in patients with moderate heart failure enalapril was efficacious and safe because of improvement of NYHA class, augmentation of exercise tolerance and low rate of clinical and laboratory side effects.