The thermal behaviour of tin(IV) 2-carboxyethylphosphonate was studied by TGA and DSC techniques under oxygen and nitrogen atmospheres. The decomposition stages are more defined in nitrogen than in oxygen, but in both cases the layered compound is stable up to around 300 degrees C. Samples treated thermally at temperatures ranging from 100 to 900 degrees C for 1 h at atmospheric pressure exhibit XRD and FTIR data suggesting the formation of Sn(HPO4)(2) as intermediate and the cubic pyrophosphate as the final product of the decomposition.