Magnetic hydrogel microspheres 1.5 mum in size were prepared by dispersion copolymerization of 2-hydroxyethyl methacrylate and ethylene dimethacrylate in the presence of magnetite, which formed the core of the particles. RNase A was coupled to the particles by the cyanuric chloride method. Gel electrophoresis of plasmid DNA pUC 19 (contaminated by bacterial RNA) confirmed RNA degradation with the immobilized enzyme. The effect of temperature and pH on the relative activity of immobilized RNase A was estimated after incubation of the samples at different temperatures (30-80 degreesC) and pH (4.0-8.0). Maximum relative activity was observed at 70 degreesC and pH 6.5. The matrices based on magnetic poly(HEMA) had a low tendency to adsorb RNA.