Fe3Pt austenites undergo an ordering reaction belowT c in addition to the martensite transformation at a much lower temperature. It is to be expected that theM s temperature will be affected by the degree of austenite order and the progress of austenite ordering can be conveniently represented by the variation ofM s temperature. In this study it was found that heat treating the annealed austenites belowT c , a single-stage ordering reaction which followed first order kinetics was observed. The ordering rate or the rate ofM s temperature change was found to be composition dependent, faster for alloy closer to the stoichiometry. The reversed austenite contains transformation induced defect structure. Consequently, heat treating the reversed austenites belowT c a two-stage reaction was observed. Annealing of defect structure was found to precede the ordering reaction. Both annealing and ordering followed first order kinetics. The salient feature during annealing was that the initial rate ofM s temperature change appeared to be independent of alloy composition.