Vanadia/alumina based catalysts have good performance in oxidative dehydrogenation of propane. The use of Multi-Track to determine the amount of highly reactive oxygen species on these catalysts was studied. Using so-called pump-probe experiments and varying the pulse size of CO could be used to quantify the amount of reactive oxygen present on the catalytic surface. A correlation between the amount of reactive oxygen was determined, and the steady state conversion of several vanadia/alumina catalysts in CO oxidation was discussed. Contaminations in the alumina support affected the amount of highly reactive oxygen species. The role of Fe in the applied alumina was illustrated on the basis of Fe-doped vanadia/alumina catalysts. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).