Aluminosilicate mesostructures (MSU-S-BEA) assembled from zeolite Beta (BEA) seeds exhibited relatively high hydrothermal stability and were significantly more active in the cracking of gas-oil compared to MCM-41 after severe steaming pretreatment. The MSU-S-BEA mesoporous, materials with wormhole framework structure and those having morphology of solid nanoparticles with high interparticle mesoporosity were more steam-stable and more active after severe steaming than those with hexagonal pore structure. Differences in acid sites strength between the MSU-S-BEA materials and MCM-41 could not be probed by the complex reaction system of the large hydrocarbon molecules of gas-oil. (c) 2005 Elsevier B.V. All rights reserved.