of 2-piperazinylbenzimidazole derivatives were prepared and evaluated as 5-HT3receptorantagonists. Their 5-HT3receptor affinities were evaluated by radioligand binding assays, and their abilities to inhibit the 5-HT-induced Bezold-Jarisch reflex in anesthetized rats were determined. Compound 7e (lerisetron, pKi = 9.2) exhibited higher affinity for the 5-HT3receptor than did tropisetron and granisetron