Highly ordered mesoporous Cr-MCM-41 materials with different Si:Cr mole ratios have been synthesized by using the hydrothermal method and avoiding co-precipitation of chromium oxides during synthesis. Detailed characterizations of these two-dimensional hexagonal mesoporous Cr-MCM-41 materials were carried out using powder XRD, TEM, SEM-EDS, N-2 sorption, FT-IR and UV-vis diffuse reflectance measurements. Cr-MCM-41 materials showed excellent catalytic activity and high selectivity in the direct oxidation of cycloalkanes viz. cyclohexane and cyclooctane to cyclohexanone and cyclooctanone, respectively, using dilute aqueous H2O2 or tert-butyl hydroperoxide (TBHP) as oxidant under mild liquid phase reaction conditions. (c) 2005 Elsevier B.V. All rights reserved.