The results of a complex investigation of V-Mg-O catalysts for oxidative dehydrogenation (ODH) of methanol are presented. The efficiency of vanadium-magnesium oxide catalysts in production of formaldehyde has been evaluated. Strong dependence of the formaldehyde yield and selectivity upon vanadium oxide loading and the conditions of heat treatment of the catalyst were observed. The parameters of the preparation mode for the efficient catalyst were identified. In optimised reaction conditions the V-Mg-O catalysts at the temperature approximate 450 degrees C ensured the formation of formaldehyde with the yield of 94% at the selectivity of 97%. No visible changes in the performance of the catalyst (methanol conversion, formaldehyde yield and selectivity) were detected during the 60 h of operation in prolonged runs. Characterization of the catalyst by XRD, IR, and UV methods suggests the formation of species of the pyrovanadate type (Mg2V2O7) with irregular structure on the surface of a V-Mg-O catalyst. These species make the catalyst efficient for methanol ODH. (c) 2005 Elsevier B.V. All rights reserved.