hoxybenzoic acid and substituted 1-piperidineethanol were synthesized and found to be potent 5-HT4receptor agonists in the electrically-stimulated myenteric plexus and longitudinal muscle of the guinea pig ileum and the rat esophagus muscle. Monosubstitution of the piperidine ring with Me, OH, NH-Ac, or CONH2 groups gave compounds equipotent to 7a (ML 10302), a 5-HT4receptor agonist previously reported