Chemical modification of the trypsin inhibitor from soya beans by a hydrophilic synthetic copolymer of N-vinylpyrrolidone was studied. The optimal conditions for modification (pH, ratio of reactants, reaction time) were established. The soluble polymeric forms of the inhibitor differing in the number of covalent bonds with the copolymer were obtained. An affinity adsorbent for isolation of trypsin was prepared by adsorption of the polymeric form on silochrome.