By reacting 0.1 mol 3-chloroethyl-5-methylpyrazole (I) with 0.2 mol 1-(3-chlorophenyl) piperazine (II), and triturating the product with ether for separation of 3-chlorophenyl-1-piperazine hydrochloride. Evaporating the ether extract, mepiprazole (as dihydrochloride) is obtained by treating with gaseous hydrochloric acid in ethanol.