The thermal decomposition behaviour of ammonium hexachlororuthenate(IV), palladate(IV), osmate(IV), iridate(IV) and platinate(IV) was investigated in nitrogen atmosphere using TG and DTA techniques. X-ray powder diffractometry was used to identify the final solid decomposition products. The thermal decomposition of the complex salts yields the respective metals as the final residue. The thermal decomposition mechanism of these complex salts is suggested and the thermal stability in the solid state is discussed in terms of inorganic energetics, such as the ligand field stabilization energy and lattice energy. The sequence of thermal stability of the complex salts was found to be Os(IV) > Ir(IV) > Pt(IV) > Ru(IV) > Pd(IV).