The Wurtz synthesis of polysilanes is a useful route in the production of polymeric precursors for silicon carbide ceramics and especially fibres. Copolymers have been synthesized by the dechlorination of methylphenyldichlorosilane and phenyltrichlorosilane in a 1 : 1 molar ratio using sodium metal dispersed in xylene. Changes have been made to the work-up procedure, leading to the separation of the various reaction products, in an attempt to improve the processing of ceramic fibres via polymeric precursors. It has been found that variation in the solvent used to separate the reaction products modified their yields and characteristic properties. Gel permeation chromatography (g.p.c.) showed that the molecular weight distribution of the soluble solid fraction, of importance as a potential precursor for ceramic fibres, had changed, which altered the softening temperature range observed. Thermomechanical analysis demonstrated that these changes could be as much as 70 degrees C, which has important consequences for the processing of ceramic fibres from these precursors. Although some small variations in the ceramic yield were observed by thermogravimetry, these did not correlate with the g.p.c. data, suggesting that their chemical structure is at least as important as their molecular weight distribution in determining this yield.