To provide a useful LHRH antagonist peptide.

The LHRH antagonist peptide is an LHRH antagonist containing a peptide compound, wherein the residue of the peptide compound corresponding to the amino acid at position 6 of natural mammalian LHRH contains D-Lys(Imdac), D-Lys(Ppic), D-Lys(Dodac), D-Lys(pGlu), D-Lys(Otac) and D-Lys(Onic) or a component selected from a dipolar component, a sulfonium component, a receptor-modifying component and a small polar component in a manner to impart the peptide compound with LHRH antagonist activity. The dipolar component is not an amphoteric ion pyridinium and the residue is not D-Cit, D-Hci or a lower alkyl derivative of D-Cit or D-Hci.

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