Vapour phase O-metbylation of the dihydroxy benzenes, catechol, resorcinol and hydroquinone with methanol has been investigated in the temperature range 573-673 K over alkali-loaded fumed silica. Fumed silica (SiO2) by itself has no O-methylation activity, but on impregnation with alkali metal oxides (Li, Na, K and Cs) becomes active for O-methylation producing mono- and dialkylated products. Activity of the catalysts and selectivity for dialkylates increase with metal loading and basicity of the metal ions (Cs > K > Na > Li). Very high conversion (similar to93%), at nearly 100% selectivity for O-methylation was obtained over Cs-loaded fumed silica in the case of resorcinol and hydroquinone. (C) 2002 Elsevier Science B.V. All rights reserved.