The present study was conducted to determine the characteristics of the effects of Keishi-ka-shakuyaku-to (Gui-Zhi-Jia-Shao-Yao-Tang; TJ-60) on diarrhea. Significant repression was noted by TJ-60 at 1000 mg/kg, p.o.for diarrhea induced by pilocarpine, barium chloride or castor oil. Under normal conditions, TJ-60 did not influence small intestinal transit by its oral treatment even at 1000 mg-kg, however, it dose-dependently improved the acceleration of such transit caused by neostigmine. TJ-60 did not influence the resting tonus in isolated small intestine, but did selectively inhibit low frequency electrostimulated contractions.These results indicate that the antidiarrheal effects of TJ-60 may be due to the inhibition of excessively accelerated small intestinal movement, and that the inhibition of acetylcholine release by parasympathetic nerves is partly involved in the mechanism of this antidiarrheal action.