The use of non-isothermal methods for finding the kinetic parameters (E, Z and DELTA-S*) and the mechanism of decomposition of the complexes, tris(orthovanilinoximate)chromium(III) and tetrakis(orthovanilin-oximate)diaquothorium(IV) is reported. The former complex decomposes regularly without any distinguishable rest in the curve while the latter decomposes with a distinguishable rest in the curve. Both the complexes involve random nucleation mechanism.