Surface biomedical effects of plasma treatment and plasma polymerization on medical-grade polyetherurethane were studied. N-2 and Ar plasma treatments and hexamethyldisiloxane (HMDS) plasma polymerization were performed at a power of 100 W with exposure times ranging from 1 to 15 min. The results showed that the contact angle of water was decreased from 79 degrees to 62 degrees by N-2 and Ar plasma treatments, and N-2 plasma treatment caused a slight enhancement in anti-coagulability and anti-calcific behavior. HMDS polymerization resulted in a decrease from 79 degrees to 43 degrees in the contact angle and an increase from 30.5 to 37.4 s in the recalcification time. At the same time, the anti-coagulability of polymerized samples for the exposure time of 2-5 min was 2.5 times that of the untreated sample. Results of XPS and ESR analyses showed that HMDS deposited onto the polyetherurethane surface and formed new Si-N bonds, and increased the number of radicals in the sample. XPS analysis also showed that Nz and Ar plasma treatments broke some of the C-O and C=O bonds at the surface and resulted in oxidation of the surface.