The Vroman effect, named after Leo Vroman, is exhibited by proteinadsorption to a surface by blood serum proteins. The highest mobility proteins generally arrive first and are later replaced by less motile proteins that have a higher affinity for the surface. A typical example of this occurs when fibrinogen displaces earlier adsorbed proteins on a biopolymer surface and is later replaced by high molecular weight kininogen. The process is delayed in narrow spaces and on hydrophobic surfaces fibrinogen is usually not displaced. Under stagnant conditions initial protein deposition takes place in the sequence: albumin; globulin; fibrinogen; fibronectin; factor XII, and HMWK.