The pseudo-biospecific affinity ligand L-histidine immobilized poly(2-hydroxyethylmethacrylate) (PHEMA) in spherical form (100-150 mum in diameter) was used for the affinity chromatographic separation of human-immunoglobulin-G (HIgG) from aqueous solutions and human plasma. The PHEMA adsorbents were prepared by a radical suspension polymerization technique. Reactive aminoacid-ligand L-histidine was then immobilized by covalent binding onto these adsorbents. Elemental analysis of immobilized L-histidine for nitrogen was estimated as 62.3 mg L-histidine/g of PHEMA. The maximum HIgG adsorption on the L-histidine immobilized PHEMA adsorbents was observed at pH 7.4. The non-specific HIaG adsorption onto the plain PHEMA adsorbents was very low- (about 0.167 mg/g). Higher adsorption values (up to 3.5 mg/g) were obtained when the L-histidine immobilized PHEMA adsorbents were used from aqueous solutions. Much higher amounts of HIgG were adsorbed from human plasma (up to 44.8 mg/g). Adsorption capacities of other blood proteins were obtained as 2.2 mg/g for fibrinogen and 2.8 mg/g for albumin. The total protein adsorption was determined as 52.1 mg/g. The affinity microbeads allowed the one-step separation of HIgG from human plasma. The HIgG molecules could be repeatedly adsorbed and desorbed with these L-histidine-immobilized PHEMA adsorbents without noticeable loss in their HIgG adsorption capacity.