Poly(ethylene terephthalate) (PET) has been reported in literature to be moderately inflammatory and thrombogenic. To moderate the inflammatory response, PET fabric was surface modified by either Fluoropassiv fluoropolymer (FC), or an RGD-containing peptide (RGD). Samples were subsequently autoclave sterilized and implanted subcutaneously in Sprague Dawley rats for 2 to 4 weeks. Retrieved samples were evaluated histopathologically for indications of material toxicity and healing. Minimal acute or chronic inflammation was associated with the fabrics after 2 and 4 week implant duration. However, fibroblast proliferation into FC modified fabric (PET/FC) was less than that into unmodified (PET) and RGD modified fabric (PET/RGD) after 4 weeks, suggesting that FC modification of PET may inhibit excessive tissue growth. Additional samples of modified and unmodified fabrics were placed in stainless steel mesh cages, which were then implanted subcutaneously for 4 weeks. Cellular exudate was extracted weekly and cell concentrations within the exudate measured. Total leukocyte count (TLC) (reflective of local inflammation) at 1 week for PET/RGD was greater than that for PET/FC and PET. TLCs after 4 week implant decreased for all sample groups. In a separate experiment, PET vascular grafts surface modified by either FC or RGD were contacted 1 h with blood using the baboon arteriovenous (AV) shunt model of thrombosis in both the presence and absence of heparin. Accumulation of 111In labeled platelets (reflective of thrombus accumulation) upon grafts was less in the presence of heparin (effect significant at p = 1.2 x 10(-6), two-way ANOVA). Accumulation (in the presence of heparin) upon PET/RGD was less (p = 0.19), and upon PET/FC significantly less (p = 0.016) than that upon the unmodified PET control, suggesting that FC modification of PET may inhibit thrombus accumulation.