The present paper investigated histological changes in the myocardium in two potential beta-adrenolytic agents, 4-[3-isopropylamino-2-hydroxypropoxy]-3-[propoxymethyl]acetophenone and 4-[3-isopropylamino-hydroxypropoxy]-3-[pentyloxymethyl]acetophenon e after intravenous administration in doses of 8 mg/kg and 24 mg/kg. It results from the found data that in both agents in the doses used there are no necrotic changes in the myocardium and the values of the impairment range within the 1st degree of Zbinden's classification, comparable to the standard metipranolol.