Peptides having high binding activity for human interleukin-1 and represented by the following formulaH-X.sup.1 -Cys-A-B-A-B-A-Ser-X.sup.2 -Ywherein each A represents an amino acid residue selected from the group consisting of Val, Leu, Ile and Nle, independent of any other selection for A; B represents an amino acid residue selected from the group consisting of Arg, Lys, Gln, His and Ser, independent of any other selection for B; X.sup.1 and X.sup.2 each is a single bond or a peptide segment comprising 1-10 amino acid residues selected from Gly, Ala, Val, Arg, Asn, Ser, Phe, Pro, Leu, Glu, Asp, Lys, Thr, His, Tyr, Nle and Ile and Y represents a hydroxyl group or an amino group; and their salts.