The purpose of this study is to analyse the flow of a linear polydimethylsiloxane of high molecular weight on plane surfaces that may interact differently with the silicone fluid used. Stainless steel surfaces and slightly rough silicon surfaces were examined, including silica surfaces where monolayers of fluorine chains were grafted on by silanation reactions. The interest and principle of these reactions are briefly recalled. The quality of the surface treatment was checked by wetting experiments. For each ''fluid-wall material'' pair, flow rate measurements were performed under a given pressure. In addition, the extrudate was photographed under various flow regimes. Combined analysis of the flow curves and observations at the die outlet helped to determine the effect of roughness and of the wall material for the specific flow conditions considered.