An investigation of adsorption from binary mixtures of fibrinogen and high molecular weight kininogen (KK) to glass is reported. Experiments were performed using radioiodinated proteins in which the adsorption of each protein was measured from serial dilutions of mixtures having a ratio of the proteins approximately the same as in plasma (fibrinogen in excess). Fibrinogen adsorption passes through a maximum as solution concentration increases, analogous to its behavior in plasma as reported previously (Brash, J. L.; ten Hove, P. Thromb. Haemostasis, 1984, 51, 326). HK adsorption increases monotonically with concentration such that fibrinogen is virtually excluded from the surface at the highest concentrations even though present in large excess. A kinetic model is developed in which initially adsorbed fibrinogen can either desorb spontaneously, relax to an irreversibly bound state, or exchange with HK. The model solution is obtained in terms of the ratio of the rate constants for exchange and relaxation, k(ex)/k(1)(’) and is independent of the nature of the available surface function. Data fits to the model are excellent and give essentially invariant values of k(ex)/k(1)(’) for different ratios of the two proteins in solution. The results of this study emphasize the importance of surface relaxation in competitive protein adsorption.