The thermal decomposition of lanthanum oxalate hydrate La-2(C2O4)(3).10H(2)O till 900 degreesC, in air, is investigated by non-isothermal gravimetry and differential thermal analyses. Intermediates and final solid products were characterized by X-ray diffraction (XRD) and IR-spectroscopy, the results show that La-2(C2O4)(3).H2O dehydrates in stepwise at 86-360 degreesC and decomposes to La2O3 at 710 degreesC through different intermediates, La-2(C2O4)(3), La2O(CO3)(2) and La2O2CO3, that form at 400, 425 and 470 degreesC, respectively. The final product La2O3 obtained at 800 degreesC has a surface area of 13.4 m(2)/g. The activation energy, DeltaE of the observed thermal processes is obtained by the non-isothermal method.