The reaction of oxygen with microporous carbons with high surface area at temperatures up to approximately 1000 K is studied using combined thermogravimetric analyzer and mass spectrometer. The study will place an emphasis on the role of the carbon-oxygen surface complex. The surface complex is the primary intermediate in carbon gasification, yet its role in the reaction is not well understood. Below 900 K, for example, the complex is stable and remains on the surface as the reaction proceeds. Above this temperature, though, the complex desorbs readily, and adsorption is presumably the rate controlling step.