The kinetics of complete oxidation of bismuth powder by air has been investigated by thermogravimetric studies under isothermal conditions in the range 729-968 K. Particles size was chosen in the 35-375-mum range. We have been able to carry out the full oxidation of the powder far above the bismuth metal melting point (544.3 K) without coalescence of the particles. A quantitative interpretation based on the diffusion of reactants through the oxide layer has been proposed. The activation energy calculated from the Arrhenius law is close to 139 kJ mol(-1).