The reinforcement of poly(dimethylsiloxane) (silicone rubber) imparted by different types of fillers was investigated. Three different techniques of incorporation of silica were compared: the usual blending process, in situ filling process, and introduction of spherical colloidal silicas (Stober silicas). In addition, results obtained with other types of fillers-layered silicates and fibrous clays-were discussed. The role of filler is assessed essentially through the mechanical properties of the silicone composites. (C) 2004 Wiley Periodicals, Inc.