(+/-)-1-Acyl-3-(3,4-dichlorophenyl)-3-[2-(spiro-substituted piperidin-1'-yl)ethyl]piperidines and their quaternary ammonium salts were prepared and evaluated for their NK1 receptor antagonistic activity. Some of these inhibited SP-induced contraction in guinea pig ileum with IC50 values at a level of 10(-9) M and showed potent inhibitory activity against selective NK1 receptor agonist-induced bronchoconstriction in guinea pigs.