It was shown that the agonists of peripheral mu-receptors DALBA and PLO17 increase the resistance of the heart to adrenaline, aconitine, ischemic, reperfusion, and CaCl2-induced arrhythmias and also raise the threshold of ventricular fibrillation in postinfarction cardiosclerosis. The antagonists of mu-receptors naloxon and STAR removed these effects. The ganglion-blocking agent hexamethonium had no influence on the antiarrhythmic effect of DALBA. It is supposed that the autonomic nervous system does not play any essential role in the mechanism of the antiarrhythmic effect of agonists of peripheral mu-receptors.