Using a heating rate of 5 degrees C min(-1), CsIO4 decomposes between 300 and 350 degrees C according to the reaction 2CsIO(4)(s) --> 2CsIO(3)(s) + O-2(g), with an enthalpy change of - 57 kJ mol(-1) CsIO4. The reaction occurs in two distinct parts. First a maximum number of nuclei (approx. 14 per mu m(2)) forms at a constant rate according to the power law. Then these nuclei grow according to the contracting area equation. Using isothermal decomposition data, an activation energy value of 226 kJ mol(-1) and In A of 40.9 were calculated for the first part of the reaction where nuclei are formed, while the activation energy value for the growth of the nuclei is 138 kJ mol(-1) and In A is 21.7. Secondary electron micrographs were used to determine the most parsimonious kinetic equation for the decomposition data.