A systematic study of the effects of polymer surface properties on the interaction with human endothelial cells (HEC) may lead to the development of small-diameter vascular grafts. HEC, suspended in culture medium containing 20% serum adhered and spread onto moderately wettable polymers such as TCPS (tissue culture polystyrene). Reduced or no adhesion of HEC was observed upon the hydrophobic polymers PETP (polyethyleneterephthalate, Dacron) and FEP (fluoroethylenepropylene copolymer, Teflon). Polymers precoated with the proteins albumin (Alb), high density lipoprotein (HDL), and immunoglobulin G (IgG) inhibited the adhesion of HEC, whereas fibronectin (Fn) coátings promoted cell adhesion. Endothelialization of PETP and FEP only occurred after precoating of these materials with Fn. The adsorption of Fn, Alb, HDL, and IgG from solutions of different serum concentrations onto TCPS, PETP, and FEP was related to the adhesion of HEC. Serum Fn only adsorbed onto TCPS, with the maximum at 0.1% serum concentration. Maximal cell adhesion onto TCPS was also observed after pretreatment with a solution containing 0.1% serum. The cell adhesion inhibiting proteins Alb and HDL preferentially adsorbed at higher serum concentrations. Desorption of these proteins and exchange for, e. g., cellular Fn may result in cell spreading and proliferation of HEC upon TCPS.