Thermal decomposition of ammonium p-tungstate (APT) to tungsten trioxide (WO3) was carried out in both batch and fluidized-bed reactors. In a batch reactor, the temperature and holding time for achieving complete decomposition were found to be much higher as compared to the respective values obtained in a fluidized-bed reactor using air as the fluidizing medium. The present studies have shown that fluidized-bed decomposition of APT offers a number of distinct advantages such as lower decomposition temperature as well as time, faster kinetics, and better product morphology. The decomposition kinetics, in the fluidized-bed reactor, was found to fit well into the "Power Law" model, d alpha/dt = k(1/r)alpha(1-r), where alpha = fraction decomposed, k = rate constant, and r (a constant) is 1/2. The activation energy of the decomposition reaction suggests the overall process to be surface controlled.