In this study, adhesion and spreading of human skin fibroblasts on gradient surfaces of dichlorodimethylsilane (DDS) coupled to glass was investigated. Gradient surfaces were prepared by the diffusion technique and characterized by the Wilhelmy plate technique for their wettability and by scanning x-ray photoelectron spectroscopy for their chemical surface composition. A linear relation between the gradient length, based on advancing water contact angles, and the square root of the diffusion time of DDS was observed. XPS analysis and the cellular experiments were carried out on gradient surfaces prepared using diffusion time of 3 h. A continuously varying chemical composition over the length of the gradient surfaces observed with the Si/O elemental surface concentration ratio being highest on the hydrophobic end of the gradient surfaces. In the presence of serum proteins, human skin fibroblasts seeded on these gradient surfaces showed a preferential adhesion onto the steepest part of the gradient, probably due to an optimal local wettability and/or local chemistry. Furthermore, it was shown that the spread area of human fibroblasts increased over the length of the gradient surface when going from the hydrophobic to the hydrophilic end. Summarizing, this study shows that the use of gradient surfaces to study cellular responses to materials surface properties, like wettability, yields more-convincing conclusions than the use of a variety of materials with different wettabilities due to the control of the specific surface chemistry of gradient surfaces. © 1995 John Wiley & Sons, Inc.