The reactivity of SiO2, MoO3/SiO2 and V2O5/SiO2 in the temperature range 400-800 degrees C and at atmospheric pressure has been thoroughly investigated by temperature-programmed reaction (TPR) measurements obtaining a continuous sequence of conversion, product distribution and reaction rate data, The effect of the contact time (0.083 less than or equal to tau less than or equal to 0.332 s) on the selectivity pattern and formaldehyde productivity (STYHCHO, g kg(cat)(-1) h(-1)) has been assessed. The onset temperature of formaldehyde formation (T-o,T-HCHO) accounts well for the reactivity of oxide catalysts in the methane partial oxidation (MPO), For all the systems studied the same sequence of onset temperature of product formation : T-o,T-HCHO < T-o,T-CO < T-o.CO2 < T-o,T-C2 proves that formaldehyde is the primary product of MPO on silica-based oxide catalysts. A suitable procedure for the calculation of conversion-selectivity data is pointed out. Full agreement between TPR data and continuous flow (CFR) and batch reactor (BR) isothermal measurements was found, The suitability of the TPR method as a fast and reliable tool for testing oxide catalysts in MPO is assessed.