Abstract: Carriers coated with a copolymer of a hydrophilic acrylate or methacrylate monomer and a copolymerizable unsaturated carboxylic acid or unsaturated amine are provided which are substantially free from nonspecific adsorption of proteins and the like. Due to the side-chain carboxyl or amino groups of the copolymer, these coated carriers are able to immobilize bio-active materials such as antigens, antibodies, complements and enzymes. These carriers, on which bio-active materials can be immobilized, are useful as clinical selective adsorbents, affinity-chromatographic adsorbents, selective electrodes or columns for analysis.