Cobalt-containing mesoporous silicates with MCM-41-like structure, with Si/Co greater than or equal to 49, are active and selective catalysts for the oxidative dehydrogenation (ODH) of isobutane. The formation of dehydrogenation products is analysed in terms of the nature of the cobalt species, tetrahedral Co(II), and heterogeneously initiated gas-phase reactions inside the mesopores. (C) 2004 Elsevier B.V. All rights reserved.