Thermal decompositions of triethanolamine complexes of Cr(III), Fe(III), Ru(III), Rh(III), La(III), Ce(III) and Nd(III) in dynamic nitrogen and air atmosphere were studied by DTA, TG and DTG. The final solid decomposition products were identified by X-ray powder diffractometry. The thermal stability of the complexes in the solid state was discussed. These complexes exhibit a considerable thermal stability and the stability order was found to be : Nd(III)> La(III) congruent to Ce(III) > Cr(III)> Fe(III)> Ru(III)> Rh(III).