AbstractAdsorption of the plasma protein fibrinogen onto electrically polarized 316L stainless steel was observed and quantified using both in situ and ex situ atomic force microscopy (AFM) techniques. Significant differences in fibrinogen adsorption were observed across voltages. Ex situ studies showed significantly lower area coverage (θ) and height of adsorbed Fb on cathodically polarized surfaces when compared to anodically polarized surfaces. Conformational differences in the protein may explain the distinctions in Fb surface area coverage (θ) and height between the anodic and cathodic cases. In situ studies showed significantly slower kinetics of Fb adsorption onto surfaces below −100 mV (vs. Ag/AgCl) compared to surfaces polarized above −100 mV. Electrochemical current density data showed large charge transfer processes (∼1 × 10−5 to 1 × 10−4 A/cm2) taking place on the 316L SS surfaces at voltages below −100 mV (vs. Ag/AgCl). These relatively large current densities point to flux of ionic species away from the surface as a major source of the reduction in adsorption kinetics rather than just hydrophilic or electrostatic effects. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2008