Glucoamylase was retained in calcium alginate gels, when the molecular weight of the enzyme was increased, e.g., by attachment to polymeric supports or by intermolecular cross-linking. Alternatively, the enzyme could be retained by covalent attachment to the alginate matrix. In the majority of the glucoamylase derivatives more than 50 % of the initial activity determined with maltose or partially hydrolyzed starch as substrate was recovered, while upon entrapment in gel particles, less than 40 % and 6 % of the initial activity towards maltose and partially hydrolyzed starch, respectively, was recovered. Thus, diffusional and steric limitations on substrate access seem to influence the apparent enzymic activity, in spite of the high permeability of calcium alginate gels. Dextran-coupled glucoamylase entrapped in calcium alginate gels has been used as a packed-bed reactor for continuous hydrolysis of oligodextrins during a period of two months with no change in activity.