SUMMARYThe binding sites of three typical calcium channel antagonists, 1,4-dihydropyridines, benzothiazepines and phenylalkylamines, were successfully identified within the primary structures of calcium channels using a photoaffinity labeling technique. The results confirm pharmacological observations of the three antagonists that had been proposed to interact allosterically with each other. We briefly review the results and discuss the future prospects. (Jpn Heart J 1996; 37: 643-650)