Characterization, thermal stability and thermal decomposition of transition metal malonates, MCH2C2O4 center dot nH(2)O (M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II)), as well as, the thermal behaviour of malonic acid (C3H4O4) and its sodium Salt (Na2CH2C2O4 center dot H2O) were investigated employing Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC). infrared spectroscopy, TG-FTIR system, elemental analysis and complexometry. The dehydration, as well as, the thermal decomposition of the anhydrous compounds Occurs in a single step. For the sodium malonate the final residue up to 700 C is sodium carbonate, while the transition metal malonates the final residue up to 335 C (Mn), 400 C (Fe), 340 degrees C (Co), 350 C (Ni), 520 C (Cu) and 450 C (Zn) is Mn3O4, Fe2O3, Co3O4. NiO, CuO and ZnO, respectively. The results also provided information concerning the ligand's denticity, thermal behaviour and identification of some gaseous products evolved during the thermal decomposition of these compounds. (C) 2009 Elsevier B.V. All rights reserved.