The anatase rutile phase transition in TiO2 in the presence of Fe2O3 was investigated in air and argon atmospheres by means of X-ray diffraction and scanning electron microscopy. Isothermal curves of rutile transformed from anatase as a function of time were obtained between 825 and 950 degrees C. The data were well fitted by various rate laws. In the presence of Fe3+, the anatase rutile transition temperature is lower and the transformation rate in air is higher than the corresponding one in pure TiO2. The transformation in the presence of Fe3+ in an argon atmosphere is more rapid than in air. The enhancement effect of Fe3+ on the anatase rutile transformation in both atmospheres is understood on the basis of the formaiton of oxygen vacanies.