A series of microspheres composed of methyl methacrylate (MMA) and N(2-hydroxypropyl) methacrylamide (HPMA), and/or 2-(methacryloyloxy)ethyl phosphorylcholine (MPC), i.e., binary copolymer microspheres [poly(HPMA-co-MMA)(KPS) and poly(HPMA-co-MMA)(ABIP)] and ternary ones [poly(HPMA/MPC-co-MMA)(KPS) and poly(HPMA/MPC-co-MMA)(ABIP)], were prepared by emulsifier-free emulsion copolymerization using potassium peroxodisulfate (KPS) or 2,2’-azobis [2-(imidazolin-2-yl)propane]dihydrochloride (ABIP) as initiators. The decrease in zeta-potential of the polymer microspheres is caused by the addition of the HPMA and/or MPC moieties. Equilibrium water content of poly(HPMA-co-MMA)(ABIP) showed a remarkable swelling change with a change in response to temperature : the hydrated conformation at 28 degrees C and the dehydrated one at above 40 degrees C. The adsorption of protein on the polymer microspheres also changed in response to change in temperature. The ternary polymer microspheres effectively suppressed the adsorption both of Alb and Glo, less than binary ones. A series of polymer microspheres are expected to apply as a novel drug carrier with both thermosensitive and nonthrombogenic functions.