In-situ stress determinations by X-ray diffraction have been performed during pure iron oxidation (p(O-2) = 2 x 10(-3) Pa, T = 800 degreesC. On yttrium implanted specimens the stress level is close to zero before oxidation. On CeO2 coated specimens, the initial compressive stress due to surface polishing is not modified by the coating. During oxidation, the in-situ compressive stress value determined in the Fe(1-x)O scale, is not strongly dependent upon the reactive element nature. Nevertheless, the stress evolution during cooling and residual stresses determined after cooling to room temperature are very different. Blank and CeO2 coated specimens show relatively high compressive stresses whereas implanted samples show low tensile residual stresses.