Strontium oxalate exists in two different forms : the neutral strontium oxalate hydrate, SrC2O4 . H2O, and the acid salt of strontium oxalate, SrC2O4 . yH(2)C(2)O(4) . xH(2)O. Depending on the concentration of oxalic acid and ammonium oxalate as precipitating agents, both forms can be obtained. At a sufficiently low pH, the stoichiometric compound SrC(2)O(4)1/2H(2)C(2)O(4) . H2O is formed. The thermal decomposition of the different strontium oxalates is studied in different atmospheres using DSC, and TGA coupled with FTIR and MS. The TGA-EGA spectra indicate that the anhydrous acid oxalate decomposes with the release of H2O, CO, CO2 and formic acid.