A polymeric precursor to SiC based on the mixture between poly(methylsilane) and tetra-allylsilane was prepared. The structural evolution by which this precursor system undergoes until its conversion to SiC was monitored by IR, Raman, C-13 and Si-29 MAS NMR spectroscopies, and by XRD techniques. Thermal and density measurements were also run. The role of the hydrosilylation reaction between Si-H and C=C moities on the ceramic conversion was also investigated. (C) 1997 Elsevier Science Ltd.33813011306