The kinetics of isothermal decomposition of potassium metaperiodate (KIO4), doped with phosphate and aluminium has been studied by thermogravimerry (TG). We introduced a custom-made thermobalance that is able to record weight decrease with time under pure isothermal conditions. The decomposition proceeds mainly through two stages: an acceleratory stages up to alpha=0.50 and the decay stage beyond. The decomposition data for aluminium and phosphate doped KIO4 were found to be best described by the Prout-Tompkins equation. Separate kinetic analyses of the alpha-t data corresponding to the acceleratory region and decay region showed that the acceleratory stage gave the best fit with Prout-Tompkins equation itself whereas the decay stage fitted better to the contracting area equation. The rate of decomposition of phosphate doped KIO4 increases approximately linearly with an increase in the dopant concentration. In the case of aluminium doped KIO4, the rate passes through a maximum with increase in the dopant concentration. The a-t data of pure and doped KIO4 were also subjected to isoconversional studies for the determination of activation energy values. Doping did not change the activation energy of the reaction. The results favour an electron-transfer mechanism for the isothermal decomposition of KIO4, agreeing well with our earlier observations. (C) 2010 Elsevier B.V. All rights reserved.