This chapter presents an extensive review of the silane coupling agent - filler - matrix resin technology available for thermoset resins and describes in detail considerable current effort in the areas of filled thermoplastic and elastomeric composites. The intent is to consider broadly the practical improvements which can be gained through the use of silanes in composites, providing an overall perspective of the literature and recent research activity. The survey is presented under the following headings - silane coupling agents; filled thermoset composites; filled thermoplastic composites; filled elastomers; and silane-modified clays. Mineral fillers available and suppliers are listed. Refs.