In this paper, the catalytic n-butane oxydehydrogenation was studied over two catalysts: undoped and Cs-doped alpha-NiMoO4. The effects of both reaction temperature and contact time on the catalytic performances were evaluated, providing a further insight about the reaction network. It is shown that 1-butene and 2-butenes isomers are primary products, being butadiene formed through a consecutive dehydrogenation step via any n-butene. Carbon oxides are also secondary products, resulting from the deep oxidation of any hydrocarbon species. but direct oxidation of butane must also be considered, particularly to CO2. The effects of cesium-doping are an increase in the butenes production with a simultaneous inhibition of the deep oxidation to CO2 species, practically not affecting the butenes to butadiene dehydrogenation step. (c) 2004 Elsevier B.V. All rights reserved.