Invertase and amyloglucosidase were entrapped in polyvinyl alc. membranes through UV irradn. of pendent styrylpyridinium groups. The influence of crosslinking on immobilization efficiency was studied using prepolymers with varied cross-linker d., the above mentioned enzymes of different mol. wt., and various substrates. It was found that the larger enzyme invertase is effectively immobilized even in polymers with very low contents of the crosslinking component. In contrast for an effective immobilization of amyloglucosidase, a higher degree of crosslinking is necessary. Although there is only a slight loss in amyloglucosidase activity, the apparent activity, esp. for the macromol. substrate starch, is low. This is contributed to a hindered diffusion of the substrates in the swollen hydrogel matrix. The influence of the diffusion is also reflected in the kinetic parameters Km and Vmax. The pH and temp. optima of entrapped amyloglucosidase are similar to those of the native enzyme in soln.