Hydrogen-influenced reductive events in the decomposition course of ammonium paratungstate (APT) were resolved by thermal analysis (TG and DTA) as a function of the heating atmosphere (air, N2 and H-2) and rate (2-20-degrees-C min-1). A kinetic characterization of the events was carried out non-isothermally. The results indicated that the reductive events begin after the complete decomposition of APT into WO3 near 400-degrees-C, and lead eventually to the formation of W0 at 700-800-degrees-C. Thus, it was concluded that a pre-calcination of APT-containing materials might develop upon reduction to monolayer-type W0 catalysts.