In this study, polysiloxane networks prepared by hydrosilylation or hydrolysis/condensation reactions were considered to be potential precursors for Si-C-O systems. Different precursors had different pyrolytic properties, which was essentially due to their molecular architecture. The kinetics parameters, such as the activation energy, E (kJ/mol) involved in the polymer-to-ceramic conversion, were investigated by thermogravimetry using a multiple heating rate kinetic method. The relationships between the molecular architecture and the precursor composition were compared to that of a linear poly(dimethylsiloxane) precursor. Solid-state 2 9 Si nuclear magnetic resonance, infrared spectroscopies, density measurements, and X-ray diffraction measurements were made on the final samples. These products were typically amorphous, with a molecular structure formed by a random distribution of different silicon sites and variable amounts of free carbon residue.