Prokopczuk A. and Pytkowski В.: Effect of inhibitors of slow calcium current on resting calcium efflux from cat papillary muscles. Acta physiol, pol., 1989, 40 (5-6): 564-568. Examination of influence of divalent cations (Co²⁺, Ni ²⁺, Mn²⁺ and organic blockers (verapamil and D600) on calcium efflux from resting mammalian myocardium shows that they either inhibit or increase transiently 45Ca²⁺ efflux, depending on the site of action. It seems that those agents whose sites of action are limited to the sarcolemma inhibit Ca²⁺ efflux. Co²⁺, Ni²⁺, verapamil and D600 belong to this group. Mn²⁺ ions which act also apparently on intracellular structures increase transiently Ca²⁺ efflux. Such a finding illustrates a diversity in mechanisms of action in a group of agents generally classified as calcium channel blockers.