Abstract : Kinetic differences, which change with the reaction progress and temperature, appear when zirconium plates of two dissimilar thicknesses are oxidized in the presence of water vapour between 1000 and 1200°C even though the oxidation mechanism is the same in each case. These differences result from a weaker relaxation from oxidation-induced growth-stresses and a higher value of the residual stresses for the thicker plates.