Abstract: Dauricine (D), an akaloid, isolated from Menispermum dauricum DC., was reported to have antiarrhythmic and hypotensive effects. The effects of dauricine on the dose—effect response of isoprenaline and Ca²⁺ and the electro-mechanic activity in cat papillary muscle were studied and compared with tetrandrine and/or verapamil, propranolol and quinidine.1. Dauricine 8×10^-5 M decreased and shifted the isoprenaline(ISO)dose—response curve to the right non-parallelly. It appears that dauricine is similar to tetrandrine and verapamil, but different from propranolol in this respect.2. Dauricine, as tetrandrine and verapamil, showed dualistic action in Ca²⁺-antagonism.3. Effect of dauricine on the electro-mechanic activity: it depressed and widened the R wave, prolonged R-T of the surface electromyogram of the papillary muscle, and its inotropic action was analogous to that of tetrandrine. It seems that dauricine possesses not only Ca-antagonistic but also "quinidine-like" action.