New structured mesoporous catalysts TiSBA15 were synthesised by grafting titanium atoms on the pore surface of various SBA15 materials by means of titanium tetrachloride in the gas phase. Site counting allowed us to optimise the experimental conditions in order to get the best selectivity and reactivity in the epoxidation of alkenes by various hydroperoxides in mild conditions (343-353 K). The silica based materials lead, in any case, to the selective formation of the epoxides with a high level of conversion over four catalytic runs. (C) 2003 Elsevier B.V. All rights reserved.