A series of 2-(4substituted-l-(homo) piperazinyi) benzimidazoles was prepared and tested for Hl-antihistaminic activity in vitro and in vivo. Most of the compounds showed antihistaminic activity and some of the 1-[2-(substituted-oxy) ethyl] derivatives exhibited potent activity. In a structure-activity comparison it was found that the oxygen atom in the 2- (substituted-oxy) ethyl group at the 1-position of the benzimidazole nucleus played an ...