To help understand the mechanism and kinetics of silane combustion, the initial steps of silane oxidation have been studied by ab initio molecular orbital theory. Geometries have been optimized at the MP2/6-31G(d) level of theory and vibrational frequencies have been computed at HF/6-31G(d); relative energies and barrier heights have been calculated at the G-2 level of theory. Silyl radical and O-2 react to form H3SiOO, which undergoes a 1,3-hydrogen shift to form H2SiOOH, via a transition state that is 17.5 kcal/mol below that of the reactants. A low barrier of ca. 4 kcal/mol separates H2SiOOH from H2SiO and OH. Hydroxyl radical can abstract a hydrogen from H2SiO to form HSiO + H2O or it can add to H2SiO to form H2Si(O)OH-both processes appear to be barrierless. The latter intermediate can lose hydrogen to form HSi(O)OH or rearrange to form HSi-(OH)(2).