Surface properties of polycarbonate and polypropylene were modified using low pressure radiofrequency argon-oxygen mixture plasma in order to increase their wettability and make them useful for biomedical applications. The effects of process variables on wettability and weight loss were studied statistically using response surface methodology. Increased surface energies were observed for both argon-oxygen plasma treated polycarbonate and polypropylene. Formation of aldehyde and hydroxyl groups on polycarbonate and hydroxyl group on polypropylene were the surface chemistry changes observed by means of Fourier transform infrared spectroscopy. Qualitative analysis of surface morphology was performed through scanning electron microscopy. A statistical model was developed relating the process variables with the responses: surface energy and percentage weight loss. The obtained statistical models were optimized to maximize the surface energy and minimize the percentage weight loss. Blood compatibility of the polymers was tested for control sample and polymers treated with argon-oxygen plasma at optimized conditions by measuring the partial thromboplastin time. Increased partial thromboplastin time (PTT) was observed for both polycarbonate (144 s) and polypropylene (149 s) after plasma treatment compared to both control samples (128 s). (C) Koninklijke Brill NV, Leiden, 2009