Using an immunoferritin-transmission electron microscopic technique, we studied the effects of C18 alkylation and fluid shear on the distribution of albumin absorbed to a segmented polyether polyurethane. Samples were exposed to 25 mg/dl albumin solution at 0, 100 or 1500 s-1 wall shear rate for 1 min. Others underwent static incubation with albumin solution for 20 mins, followed by exposure to phosphate buffered saline at 0, 100 or 1500 s-1 for 1 min. Significant increases in uniformity and density of the albumin adsorbate were observed for all C18 alkylated surfaces, at all wall shear rates. C18 alkylation also significantly decreased the rate of shear-induced desorption of albumin. Results suggest that C18 treatment may promote the rapid development and retention of an endogenous albumin layer for blood contacting materials.