Polyaminoetherurethaneureas bearing tertiary amino groups in the main chain (M-PAEUU) were synthesized, quaternized (Q-M-PAEUU) and heparinized (H-M-PAEUU). With increasing portions of diisocyanate and with decreasing portions of polyaminoether in the feed, M-PAEUU containing more hydrogen-bonded urea carbonyl groups was prepared. With increasing hydrogen-bonding character of M-PAEUU, the adsorbed bovine serum albumin (BSA) was more denatured. By quaternization of M-PAEUU, the protein adsorption increased, but the denaturation of adsorbed proteins was suppressed. With increasing ratio of hydrogen-bonded urea carbonyl groups in Q-M-PAEUU, the adsorptions of BSA, bovine serum y-globulin ( B S ) , and bovine plasma fibrinogen (BPF) were decreased, but the degree of denaturation of adsorbed proteins was increased. In the adsorption to H-M-PAEUU, both the amount and the degree of denaturation of adsorbed proteins were strongly decreased. The dynamic adsorption experiments of plasma proteins showed the behaviors which are similar to the equilibrium adsorption experiments. The decrease of hydrogen-bonded urea linkages and the increase of hydrophilicity by quaternization and heparinization of the polymer surface may be favorable for building up a hydration layer on the surface, thus suppressing the denaturation of plasma proteins which may trigger blood clotting and thrombus formation.