The oxidation of pure rhenium was examined from 600 to 1400°C in oxygen/argon mixtures. Linear weight-loss kinetics were observed. Gas pressures, flow rates, and temperatures were methodically varied to determine the rate-controlling steps. The reaction at 600 and 800°C appeared to be controlled by a chemical-reaction step at the surface; whereas the higher-temperature reactions appeared to be controlled by gas-phase diffusion of oxygen to the rhenium surface. Attack of the rhenium appeared along grain boundaries and crystallographic planes.