We attempted to characterize the antidiarrheal action of Hange-shashin-to (TJ-14), a kampo medicine, by comparing its action with that of loperamide. The oral administration of TJ-14 caused the dose-dependent suppression of castor oil-induced diarrhea at 250 to 1000 mg/kg. No significant repression was noted by TJ-14 even at 1000 mg/kg, p.o. for diarrhea induced by pilocarpine, serotonin or barium chloride. Oral treatment with loperamide at 5 mg/kg markedly suppressed diarrhea induced by castor oil and barium chloride. Contractions of isolated guinea pig ileum in response to acetylcholine (1 x 10(-7) g/ml), histamine (1 x 10(-7) g/ml) or barium chloride (3 x 10(-4) g/ml) were little affected by TJ-14 at 10(-4) g/ml. The responses elicited by the three contractive drugs were dose-dependently suppressed by loperamide. TJ-14 did not affect the small intestinal transit even at an oral dose of 1000 mg/kg. On the other hand, the small intestinal transit was significantly suppressed by loperamide (5 mg/kg, p.o.). These results indicate that TJ-14 can effectively control castor oil-induced diarrhea, and that its antidiarrheal action was not based on the suppression of intestinal motility.