Abstract: The calcium antagonistic actions of atropine (Atr) and verapamil (Ver) were studied on the contraction of rabbit thoracic aorta strips induced by CaCl₂ and KCl. Both Atr and Ver were found to depress the contraction as demonstrated by the shift-to-right of the dose--effect relationship curves and the decrease of maximal responses, with the value of pD₂ being 4. 4 and 5.8 respectively. The intracellular Ca²⁺-dependent component of NE-induced aortic strip contraction was also inhibited by the 2 drugs, but the extracellular Ca²⁺-dependent component was barely or not inhibited by Atr before its concentration was raised to 100 μmol/L. These results indicate that the depressive effect of Atr on aortic contraction is mainly exerted by acting on the PDC (potential-dependent channel). The action of Atr on proliferation of cells was also studied in rabbit aortic smooth muscle cell (ASMC) culture. The growth was inhibited by Atr when Ca²⁺ was present in the medium. When Ca²⁺ was absent, however, the growth was stimulated by Atr 20. 6～185.2 μmol/L, but inhibited by Ah 555.7～1666.7 μmol/L, suggesting that Ca²⁺ is somehow involved in the action of Atr on ASMC growth.