Bacterial adhesion is a central step in infection on biomaterial surfaces; however, the relation between biomaterial surface properties and adhesion remains poorly understood. To quantitatively determine the relationship among polyurethane surface properties, protein coating, and adhesion, we have compared attachment and detachment kinetics of Staphylococcus aureus on three different novel polyurethanes with different protein coatings. Rate constants for attachment or detachment were measured as a function of shear rate in a well-defined laminar flow field. The tested polyurethanes included a relatively hydrophobic-base polyether urethane and hydrophilic anionomer and cationomer analogs of the base material. Materials were tested bare, or coated with human fibrinogen, plasma, or albumin. The results suggest that the presence of fibrinogen or plasma greatly enhance the attachment rate constants and decrease the detachment rate constants on all materials. The most extreme differences among the different materials were observed on the bare materials, with the base polyurethane being most resistant to both attachment and detachment. However, except for a reduced attachment rate constant on the plasma-coated sulfonated polyurethane, few differences in the rate constants were observed among protein-coated materials, suggesting the primary role of surface properties is masked by the presence of the adsorbed protein layer.