Lithographically defined substrates offer unique opportunities for the study of cell behaviors, by allowing the presentation of controlled cell stimuli. We have investigated the effects of substrate topography on the behavior of human corneal epithelial cells using substrates patterned with grooves and ridges of well-defined dimensions: On each substrate, we included feature sizes ranging from the micrometer to the nanometer scale. This work was motivated by the fact that the surface that underlies epithelial tissues in vivo, the basement membrane, has a rich topography with features of nanoscale dimensions. We found that cells responded to topographic features as small as 70 nm wide by aligning with the pattern direction. Additionally, substrate topography affected internal organization of the cell, inducing the alignment of cytoskeletal elements (actin filaments) and adhesive structures (focal adhesions). Therefore, synthetic topographies with feature dimensions of the same length scale as the features encountered in native basement membrane profoundly affected epithelial cell behavior. These findings have relevance in tissue engineering and in the design of prosthetic devices. (C) 2003 American Vacuum Society.