This invention provides pyrimidine derivatives represented bya formula,(see formula I)in the formula,ring A stands for carbocyclic group or heterocyclicgroup,X1 stands for hydrogen, lower alkyl, amino, etc.,X2 stands for hydrogen or lower alkyl,Y stands for a direct bond or sulfur or nitrogen,n stands for an integer of 0 - 4, andAr stands for a group of the following formula,(see formula II)or a salt thereof, which concurrently exhibit 5-HT1A agonistic activityand 5-HT3 antagonistic activity and are useful for therapy andtreatments of diseases such as IBS.The invention furthermore provides a therapeutic method ofIBS, characterized by having 5-HT1A agonistic activity and 5-HT3antagonistic activity work simultaneously and cooperatively in vivo,which comprises either administering 5-HT3 antagonistic agentwhich concurrently exhibits 5-HT1A agonistic activity, oradministering 5-HT1A agonistic agent and 5-HT3 antagonistic agentsimultaneously, in sequence or at an interval.
