The effect of lofexidine, clonidine, and other drugs on castor oilinduced diarrhea in rats was investigated. Castor oil was administered orally and drugs were administered intraperitoneally. The results were as follows. 1. Lofexidine(0.1-43{mu}mol$/kg) blocked dose dependently caster oil-induced diarrhea like clonidine, but its potency was weaker than that of clonidine, 1. Yohimbine (1-10{mu}mol/kg$) antagonized the antidiarrheal action of lofexidine and clonidine. 3. Prazosin (3-30{mu}mol/kg$) did not antagonize the antidiarrheal action of lofexidine and clonidine. 4. Metoclopramide, bromocriptine mesylate, and nadolol did not affect antidiarrheal action of lofexidine significantly. 5. Loperamid prolonged the antidiarrheal action of lofexidine.