A series of 1-(4-fluorophenyl)-4-(1-piperidinyl)-1-butanones substituted with benzimidazole, benzotriazole, or quinoxaline at the 4 position of the piperidine ring was synthesized and subjected to neuroleptic tests. Neuroleptic activities of several compounds were comparable to those of haloperidol. In particular, 4-[4-(2,3-dihydro-2-thioxo-1H-benzimidazol-1-yl)-1-piperidinyl]-1-(4-fluorophenyl)-1-butanone (10) was characterized by having a potent neuroleptic activity with less liability to the extrapyramidal side effect.