Poly(2-hydroxyethyl methacrylate) (poly(HEMA)) membranes were prepared by W-initiated photopolymerization of HEMA in the presence of an initiator (a-a’-azobisisobutyronitrile, AIBN). An affinity dye, i.e. Cibacron Blue F3GA (CB) was incorporated covalently and then complexed with Fe(III) ions. The polyHEMA-CB and polyHEMA-CB-Fe(III) derivatized membranes were used in the adsorption of catalase (CAT). The enzyme-loading capability of the Fe(III)-containing membrane (23.6 mu g/cm(2)) was greater than that of the poly(HEMA)-CB derivatized membrane (17.1 mu g/cm(2)). The adsorption phenomena appeared to follow a typical Langmuir isotherm. The K-m values for both immobilized catalases (poly(HEMA)-CB-CAT (22.4 mM) and poly(HEMA)-CB-Fe(III)-CAT (19.3 mM)) were higher than that of free enzyme (16.5 mM). Optimum operational temperature was 5 degrees C higher than that of the free enzyme and was significantly broader. A similar observation was made for the optimum pH. Operational, thermal and storage stabilities were found to increase with immobilization, especially in the presence of Fe(III). It was observed that enzyme could be repeatedly adsorbed and desorbed without significant loss in adsorption capacity or enzyme activity.