Abstract: In this paper, we report the synthesis and analgesic activities in mouse hot plate test and writhing test of some analogs of U- 50488, a κ-agonist. Results showed that compounds in which the amino group was pyrrolinyl had higher κ-agonist activity and the substitution of two chlorine atoms in 3 and 4-positions of the benzene nucleus was very important to κ-activity. Furthermore, all of compounds in which the amino group was piperidyl, piperazinyl or morpholinyl exhibited very weak κ-agonist activity.