Attempts have been made in the utilisation of flyash as a filler for elastomers as it is a waste product from thermal power stations, generated in huge quantities and has disposal problems. It has been used as a filler for rubbers and plastics to a very small extent, although flyash does not contribute at all in enhancing mechanical properties of composites. The purpose of this study was to obtain better utilisation of flyash as a filler, by treating it with silane coupling agent Si-69 i.e. Bis (3-triehtoxysilypropyl) tetrasulphide. Composites of chloroprene rubber containing treated and untreated flyash were made with varying proportions. A two-roll mill was used for dispersing the filler in the rubber and compression moulding was used to cure the compounded material in sheet form. Tensile properties were measured on a computerised Universal Testing Machine using the ASTM procedure. Comparison of properties of composites filled with treated and untreated flyash established that the silane treatment of flyash imparted better reinforcing properties. Tensile strength was improved by ten times whilst modulus at 400;and Youngs modulus were improved by 7.5 and 9 times, respectively at a volume fraction of about 0.5.