The application of physical stimuli to cell populations in tissue engineering and regenerative medicine may facilitate significant scientific and clinical advances. However, for the most part, these stimuli are evaluated in isolation, rather than in combination. This study was designed to combine two physical stimuli. The first being a microstructured tissue culture polystyrene substrate, known to produce changes in cell shape and orientation, and the second being laminar shear stress in a parallel plate flow chamber. The combined effects of these stimuli on endothelial cell monolayers cells were evaluated in a parallel plate flow chamber and using a computational fluid dynamics (CFD) model. The topography of the cell monolayers cultured on different microstructured surfaces was determined using confocal laser scanning microscopy (CLSM), and this topographic information was used to construct the CFD model. This research found that while the specific underlying structures were effectively planarized by the cell monolayer, significant differences in cell shape and orientation were observed on the different microstructured surfaces. Cells cultured on grooved substrates aligned in the direction of the grooves and showed higher retention after 1-h LSS conditioning than those cultured on pillars. The modeled shear stress distributions also showed differences. While minor differences in the magnitude of shear stress were noted, aligned cell monolayers experienced significantly lower spatial gradients of shear stress when compared with cells that were not pre-aligned by surface features. The results presented here provide an analysis of how one form of physical stimulus can be moderated by another and also provide a methodology by which the understanding of cell responses to topographic and mechanical stimuli can be further advanced. Biotechnol. Bioeng. 2011;108: 1148-1158. (C) 2010 Wiley Periodicals, Inc.