Thermogravimetric analysis (TGA) with simultaneous differential thermal analysis (DTA) of R2SnL2 (R = methyl (1), n-butyl (2), n-octyl (3) and phenyl (4)) and R3SnL (R = methyl (5), n-propyl (6), n-butyl (7) and phenyl (8); L = anion of 5-amino-3H-1,3,4-thiadiazole-2-thione) show that in air and nitrogen, diorganotin(IV) thiadiazolates decompose in a different manner, whereas triorganotin(IV) thiadiazolates decompose in a similar way. The decomposition of di- and triorganotin(IV) thiadiazolates occur in two or three steps. The first step of decomposition corresponds to the loss of a ligand/a part of ligand moiety, which is followed by the loss of remaining ligand moiety (in case of diorganotin(IV) thiadiazolates) and the organic groups attached to tin. In case of compounds (3) and (5), tin is partially lost to the gas phase due to sublimation. The residues obtained by thermal decomposition of these compounds are SnS and/or Sn in nitrogen and SnO2 in air, which are characterized by infrared (IR), far-infrared (far-IR), X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Mathematical analysis of thermogravimetric analysis data shows that the first step of decomposition in compounds (4), (6) and (8) in both air and nitrogen follows first order kinetics. Kinetic and thermodynamic data, such as energy of activation (E*), pre-exponential factor (A), entropy of activation (S*), free energy of activation (G*) and enthalpy of activation (H*) of the first step of decomposition have also been calculated. (C) 2005 Elsevier Ltd. All rights reserved.