We have previously described the development of a two-dimensional computational model of platelet deposition onto biomaterials from flowing blood (Sorensen et al., Ann. Biomed. Eng. 27:436-448, 1999). The model requires estimation of four parameters to fit it to experimental data: shear-dependent platelet diffusivity and three platelet-deposition-related reaction rate constants. These parameters are estimated for platelet deposition onto a collagen substrate for simple parallel-plate flow of whole blood in both the presence and absence of thrombin. One set of experimental results is used as a benchmark for model-fitting purposes. The "trained" model is then validated by applying it to additional test cases from the literature for parallel-plate Poiseuille flow over collagen at both higher and lower wall shear rates, and in the presence of various anticoagulants. The predicted values agree very well with the experimental results for the training cases, and good reproduction of deposition trends and magnitudes is obtained for the heparin, but not the citrate, validation cases. The model is formulated to be easily extended to synthetic biomaterials, as well as to more complex flows.