In this article we review the adsorption of plasma proteins onto polymer latices on the basis of our experimental data. First, the surface characteristics of the latices were examined. Hydrophilic polymer layers (water-soluble polymer layers) were found to exist on the surfaces of copolymer latices, e.g., a polyacrylamide (polyAAm) layer existed on the surface of the styrene/acrylamide copolymer [P(St/AAm)] latex. These diffuse layers strongly affected the protein adsorption, that is, the amount of plasma proteins adsorbed onto copolymer latices (viz. P(St/AAm) and styrene/2-hydroxyethyl methacrylate copolymer [P(St/HEMA)] latices), particularly in the alkaline pH region, was much smaller than that onto a hydrophobic polystyrene (PS) latex. The protein adsorption was also studied as a function of pH, ionic strength and electrolyte concentration. Further, the adsorbability of heat- and urea-denatured albumins was investigated. A higher affinity of denatured components for polymer latices was observed compared with that of the native components.