The effect of interfacing fresh pig blood with polydimethylsiloxane (PDMS) samples of different surface energies and chemistries is presented. PDMS-treated surfaces were obtained using oxygen plasmas. Aging in air produced rather hydrophobic surfaces, although less hydrophobic than the untreated one, due to hydrophobic recovery. Aging in water hindered it, therefore the surface remained hydrophilic. The concentration of albumin and fibrinogen was measured as a function of contact time with fresh pig blood with untreated, treated and aged in air, and treated and aged in water surfaces. The albumin concentration changed in a constant fashion. Fibrinogen depletion was observed for both treated surfaces. In the case of most hydrophobic surface a 'passivating layer' was formed. The same effect was not possible for the hydrophilic surface, due to the low albumin/fibrinogen-treated surface fracture energy.