A VPO catalyst prepared in an organic medium has been studied by in situ laser Raman spectroscopy for n-butane oxidation to maleic anhydride. Data could be obtained at low laser power and brief collection times. Raman characterization during continuous flow (steady-state) studies revealed that (VO)(2)P2O7 was present. Sequential oxidizing (10% O-2 in N-2) and reducing (2% n-butane in N-2) conditions were explored at 350 degrees 0 and 400 degrees 0. These cycling (unsteady-state) operations revealed that formation of V(5(+)) phases was enhanced during oxidizing conditions. The intensity of Raman bands due to (YO)(2)P2O7 increased during reducing conditions.