In order to clarify the action of a proprietary drug "Rokushingan"on cardiac function, conjugation action of its componental crude drugs (Bufonis, Bezoar, Moschus, Borneo-Camphora, Realgar, and pearl powder) was examined. All these crude drugs effected contraction of the coronary vascular system, while Bufonis alone effects selective contraction of the excised heart, indicating that Bufonis is responsible for the principal action of Rokusingan. Conjugation effect of the componental crude drugs was examined with the papillary Muscles of a cat and a rabbit, and the contraction of papillary muscles by Bufonis was found to be inhibited by the combined use of Moschus, Bezoar, and Realgar. This fact suggests that the crude drugs contained in Rokusingan show the effect not appreciable by each of them alone but by their conjugation effect.