The characteristics of a phospholipid surface are of major importance in the activation of factor X in the presence of tissue factor-factor VIIa (TF-VIIa) complex. A possible tool which provides a measure of the surface corrugation and roughness is the fractal dimension analysis. This paper uses the fractal characterization of a phospholipid surface to develop a model for analyzing surface based enzymatic reaction data. The modeling indicates that the fractal dimension (D) of a phospholipid surface is a function of the wall shear rate. The results also indicate that the fractal dimension of the phospholipid surface decreases from approximately 2.9 to 1.4 as the wall shear rate increases from 50 to 1600 sec(-1). At the same time the factor Xa production increases from 1.9 to 5.8 pmoles/(min. cm(2)). The results of the fractal dimension analysis clearly indicates that the surface roughness of a phospholipid surface may have a significant effect on factor X activation.