The propane ammoxidation reaction is investigated on an alumina-supported Sb-V-O catalyst with an Sb/V atomic ratio of 1 at nominal Sb + V monolayer coverage on alumina support. The roles of reaction temperature and of the partial pressure of reactants in the reaction are evaluated. Fresh and used catalyst is characterized by X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The effect of sudden changes in reaction feed is used to understand if the transient activation of the catalysts during the first hours on-stream is due to surface intermediates or to a change in the catalyst structure. A discussion is presented about the reaction network and the nature of the active phases.