In this study protein adsorption was monitored under well-defined and nearly uniform flow conditions at the test surface. The adsorption profiles observed demonstrated that both tightly and loosely bound proteins may be present on the surface. An understanding of these differently adsorbed species is useful since it appears that they mediate the blood response to artificial materials. The change of characteristic peak positions observed for fibrinogen on germanium and Biomer surfaces may be significant if these spectral differences can be related to changes in protein structure and the in vivo performance of different biomaterials. Finally, the ability to study competitive adsorption is important since advances in this area may eventually led to an understanding of the role adsorbed proteins play in whole blood contact with artificial surfaces.