Small-diameter vascular grafts rapidly fail after implantation, due to occlusion caused by thrombosis. This problem cannot be overcome using medication. A promising improvement of graft patency is the seeding of endothelial cells (EC) on the luminal surface of the vascular graft. Conjugates of albumin and heparin, which were developed to obtain nonthrombogenic coatings, could form an ideal coating for vascular grafts. Besides presenting anticoagulant function, heparin will bind proteins with cell adhesive properties, thus facilitating adherence of EC to the graft surface. EC were able to grow to confluency on CO2 gas plasma–treated polystyrene (PS-CO2) coated with albumin-heparin conjugate. CO2 gas plasma treatment resulted in the introduction of functional groups at the surface (e.g., hydroxyl, aldehyde, carboxylic acid, and epoxide groups). Addition of albumin-heparin conjugate to the functionalized surface in an aqueous solution with pH 8.2 yielded a stable monolayer of covalently bound conjugate. The number of cells adhering and proliferating on this surface was comparable to the number of cells on fibronectin-coated PS-CO2. However, the structure and size of EC proliferating on surface-immobilized albumin-heparin was more irregular. Long-term adherence might be improved by adding fibronectin to the albumin-heparin surface, either as a mixture with albumin-heparin or in a separate incubation step.