Three new 5-chloro-8-quinolinol derivatives such as 5-chloro-7-[4-(2-N-pyrrolidylethyl)-1-piperidylmethyl]-8-quinolinol 5-chloro-7-[4-(2-N-piperidylethyl)-1-piperidylmethyl]-8-quinolinol and 5-chloro-7-[4-(2-N-morpholinylethyl)-1-piperidylmethyl]-8-quinolinol were synthesized and found to be effective against Entamoeba histolytica in vitro and against experimental intestinal amebiasis in rats.