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 2.3×10^(-5)SM on isolated frog heart showed a slight decrease of the amplitude of motility, and the heart motility stopped in 3.5×10^(-4)M. With the administration of erythrosine 3.4×10^(-4)M, the isolated rabbit duodenum showed a remarkable contraction and this effect was inhibited by atropine 1.4×10^(-7)M. The administration of erythrosine 2.3×10^(-3), produced a contractile effect on the isolated rabbit uterus, and the motility of 6.9×10^(-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 20㎎/㎏ on mice intestinal motility were not significantly different from this of the normal control. With 20 and 40㎎/㎏ 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 40㎎/㎏, induced by C.N.B. 30㎎/㎏ showed the decrease of 57 and 78% respectively in contrast with the normal control group.