Polyethylene oxide (PEO) was incorporated into the surface of Dacron (PET) vascular prosthetic material (crimped Bionit I, BNI) followed by covalent attachment of an endothelial cell (EC) adhesion peptide: Gly-Arg-Glu-Asp-Val-Tyr (GREDVY). This procedure provides the possibility of a surface selective for EC adherence. Optimal PEO incorporation with minimal fiber damage was achieved from 78% (vol) trifluoroacetic acid (TFA) as characterized by scanning electron microscopy, nuclear magnetic resonance, bromphenol blue staining, and tensile testing. By weight, there was 4.4 times as much 18.5kD PEO as 1.5kD PEO incorporated into PET, but there were 2.8 times as many molecules of low molecular weight PEO. Attachment of 125I-GREDVY to substrates increased as follows: BNI < BNI – 18.5 kD PEO < BNI – 1.5 kD PEO. Polyethylene oxide size affected EC binding with high molecular weight material decreasing binding and low molecular weight PEO increasing attachment. GREDVY modification of BNI or either of the two BNI-PEOs gave small but consistently increased EC binding compared with the same preparation without GREDVY. In contrast, human fibroblasts cultured from umbilical vein showed decreased binding when GREDVY was attached to BNI or PEO modified BNI. These results indicate that selective EC binding to PET vascular prostheses can be achieved.