Infusion of esmolol (50-300 mcg/kg/min, mean 119-/+75.5 mcg/kg/min, average duration 3.2-/+1.22 h)) was carried out in 49 streptokinase treated patients within 6 hours of myocardial infarction. Infusion was associated with slowing of heart rate and lowering of mean dynamic systolic blood pressure (by 22%). No changes of stroke volume and index occurred. Complications requiring either cessation of infusion or decrease of its rate developed in 14.3% of patients (lowering of systolic blood pressure below 100 mm Hg in 5, complete atrio-ventricular block in 2) as a rule in the beginning of the infusion.