The solid and gaseous products from the silation of partially dehydroxylated gamma-alumina with chlorotrimethylsilane have been determined for a wide range of pretreatment and reaction conditions. Unexpectedly and contrary to previous assumptions, in all cases there was no HCl produced. Methane was the only gaseous product detected for silation reactions up to 500 degrees C. Under very severe conditions a very small amount of higher hydrocarbons was also obtained. The silating reagent is first irreversibly adsorbed by reaction with coordinatively unsaturated aluminum cations and oxygen anions, Subsequent reaction of the silyl methyl group with isolated, highly acidic hydroxyls affords the methane product.