The effects of erythrosine on motility of frog heart, rabbit duodenum and uterus isolated, and on mice intestinal motility and voluntary activity were investigated. The effect of erythrosine $2.3{ imes}10^{-5}M$ on isolated frog heart showed a slight decrease of the amplitude of motility, and the heart motility stopped in $3.5{ imes}10^{-4}M$. With the administration of erythrosine $3.4{ imes}10^{-4}M$, the isolated rabbit duodenum showed a remarkable contraction and this effect was inhibited by atropine $1.4{ imes}10^{-7}M$. The administration of erythrosine $2.3{ imes}10^{-3}M$, produced a contractile effect on the isolated rabbit uterus, and the motility of $6.9{ imes}10^{-3}M$ started to increase in contractions at first and finally stopped, keeping in continuous contractions. The effects of erythrosine 0.5, 1.0, 10, and 20mg/kg on mice intestinal motility were not significantly different from this of the normal control. With 20 and 40mg/kg of erythrosine, the effects on voluntary activity showed the decrease of 21 and 58% respectively, and voluntary activity of the mice pretreated with erythrosine 20 and 40mg/kg, induced by C. N. B. 30mg/kg showed the decrease of 57 and 78% respectively in contrast with the normal control group.