In this work, the effect of reaction conditions of oxidative dehydrogenation of propane on V2O5 reducibility along the catalytic bed was studied. Extreme conditions of catalytic test (high temperature, P-O2/P-C3H8 ratio =1) have been used. After the catalytic test. V2O5 original orange color changed along the catalytic bed. Thus, three portions differentiated by their color were picked up separately and analyzed by XRD and XPS. The reduction of V2O5-V2O3 along the catalytic bed was observed by XRD: while Surface reduction from V5+ to V3+ was also detected by XPS. Assuming that V5+-V4+ redox couple plays a key role in oxidative dehydrogenation reactions, it is concluded that the choice of reaction conditions is very important in order to avoid an excessive reduction of vanadium ions and obviously, to analyze the results properly. (C) 2003 Elsevier Science B.V. All rights reserved.