Incorporation or grafting of gallium atoms in/on mesoporous SBA-15 silicas was carried out using four different procedures. The structure and texture of the materials obtained were characterised by classical methods (X-ray diffraction, TEM, porosimetry measurements, XPS, Ga-71 NMR spectroscopy). Acidity of the solids was evaluated by ammonia adsorption, TPD of this gas and FTIR spectroscopy of adsorbed probes (2,6-dimethylpyridine and deuterated acetonitrile). Catalytic activity was tested first in the isomerisation of alpha-pinene and second in the oxidative cleavage of cyclohexene oxide. In this latter case, the results are compared with those obtained in the presence of Al-SBA-15 catalysts prepared under similar conditions. (C) 2006 Elsevier B.V. All rights reserved.