The cure and pyrolysis behavior of a Blackglas(TM) resin and Nextel(TM) 440 impregnated with Blackglas(TM) resin were studied. Cure of the Blackglas(TM) resin is an exothermic process and DSC studies indicate that with an increase of catalyst content from 0.1 to 1.0%, the onset and peak temperature of cure are decreased coupled with an increase in the enthalpy of cure indicating a greater extent of cross linking. However, pyrolysis char yield of the pyrolyzate is relatively insensitive to cure conditions. Cure pressure and pyrolysis environment are variables in the processing of Blackglas(TM) matrix composite reinforced with Nextel(TM) 440 plain weave fabric. Variations in cure pressure from 30 to 80 psi had no discernible effect on the chemistry of the pyrolyzate. However, the higher cure pressure resulted in top and bottom ply damage. Pyrolysis in an Ar environment resulted in incorporation of up to 12 wt % C of which 8 wt % was graphitic in nature in the ceramic matrix. Pyrolysis in NH3 resulted in 3.9 wt % nitrogen and 1.5 wt % carbon in the matrix, with all the nitrogen and carbon bonded to Si. The cured panels have to be pyrolyzed/densified between 6-7 times to achieve required density and porosity content. Oxidation behavior of the composites at 1000 degrees C indicate that the argon pyrolyzed CMC＇s lose more weight due to decomposition of the pyrolytic carbon, whereas, NH3 pyrolyzed CMC＇s are stable as both the N and C are bonded to Si in the matrix. Dielectric constants K＇ and K" measured at 1 GHz in the as-processed condition are high in the argon pyrolyzed CMC, (K＇ = 11-28) due to the presence of pyrolytic carbon. On the other hand NH3 pyrolyzed CMC exhibit low dielectric constant (K＇ = 4). On oxidation, the dielectric constant in both the Ar and NH3 pyrolyzed panels is approximately 4.0.