[en] Some of the work carried out at our laboratories on the immobilisation of biocatalysts onto graft copolymers prepared by radiation induced procedures is reported. The graft copolymers used were based either on hydrophilic natural polymer (agar) or on hydrophobic (polyethylene) supports. The comonomers grafted branches include poly(hydroxyethyl methacrylate) and poly(hydroxyethyl methacrylate) crosslinked with trimethylpropane triacrylate (TMPTA). The suitability of these graft copolymers for immobilising α-chymotrypsin, glucose oxidase and trypsin was assessed by determining the amount of biocatalysts coupled to the support and its retention of activity. The Michaelis Menten constants (K_M) for some of the immobilised enzymes were determined. (author)