The thermal decomposition of NaClO3 in the presence of metal oxides was studied using thermogravimetric analysis. A number of metal oxides were prepared to have comparable surface areas, and their catalytic effects on NaClO3 decomposition were compared. It was found that the catalytic activity depends on the electron configurations of the metal cations. Oxides containing metal cations with partially filled d-orbitals are all active catalysts for NaClO3 decomposition. Transition metal cations with no d-electrons are moderately active. Metal oxides containing metal cations with completely filled d-orbitals or noble gas configurations have very little activity.