Experimental facts, proving the presence of M3-cholinoreceptros in parasympathetic regulation of heart, are reviewed. Results of molecular biological and biochemical studies, showing existence of M3-cholinoreceptors in myocardium, are discussed. Physiological data, that demonstrates changes of action potential configuration due to M3-receptors activation, specific potassium current, linked with M3-receptors stimulation, and other evidence of functional importance of M3-receptros in myocardium, is analyzed. Studies dealing with cardioprotective role of M3-receptors are reviewed with special attention. The review widens our knowledge about molecular mechanisms of parasympathetic heart regulation.