The dependence of the activity of trypsin immobilized in polyacrylamide hydrogel on the hydrogel swelling ratio, the size distribution of its pores, and the means of enzyme binding has been studied. It has been shown that the most favorable conditions for immobilized trypsin are provided upon its binding to hydrogel via trypsin macromonomer copolymerization with acrylamide and a linking agent in the presence of a modifier that limits polymer chain growth.