The formation of silica−surfactant mesostructures has been studied under various acidicconditions using tetraethyl orthosilicate and hexadecyltriethylammonium bromide. Thesynthesis conditions have been optimized in order to obtain the cubic (Pm3n) mesoporousmolecular sieve designated as SBA-1 of high quality. The pore diameter of the SBA-1 materialhas been controlled within the range of 1.4−2.7 nm by expanding the surfactant micelleswith 1,3,5-trimethylbenzene or substituting the hexadecyl group of the surfactant with othern-alkyl groups (C12H25 to C18H37).