A peptide derivative having analgesic activity represented by the following formula: <IMG> wherein Q represents D-Arg or L-Arg; and X represents for example NR6-CHR7R8. Typical compounds include H2NC(NH)-Tyr-D-Arg-Phe- NHCH2CH2COOH and H2NC(NH)-Tyr-D-Arg-Phe-NHCH2CH2CONH2.
