The insoluble collagen fraction (ICF) prepared from bovine nasal cartilage was chemically modified with acetic anhydride, glyoxal or glycine methyl ester in the presence of water-soluble carbodiimide. Chondroitinsulfate C (ChS-C), cartilage proteoglycan (PPL of Schubert s preparation), RNA, albumin r-globulin, or cytochrome c was applied to ICF- or modified ICF-column at pH 3.40 (at pH 7.30 for cytochrome c), and the column was eluted by the pH gradient elution (pH 3.40-7.30) followed by linear NaCl gradient elution (0-1.0 M) at pH 7.30. When smaller amounts of ChS-C were applied to ICF-column at pH 3.40, ChS-C was eluted only by NaCl gradient elution at pH 7.30. With the increasing doses of ChS-C applied to ICF-column, the NaCl-eluted peak of ChS-C was increased to reach the maximum, and then the ChS-C peaks eluted in weakly acidic range began to appear. The elution patterns of biopolymers from ICF- and modified CF-columns appeared to be associated with the nature and number of dissociable acidic and basic groups distributed on the surface of respective species of those macromolecules. Three polar (acidic, neutral, and basic) regions on the ICF fibrils, assumed from uneven distribution of acidic and basic amino acid residues of collagen polypeptide chains10> are proposed for reasonable interpretation of the elution patterns of the biopolymers possessing different pI values from the columns of ICF and modified ICFs, which display pH-dependent bifunctional ion exchanger property.