Secondary ion mass spectrometry (SIMS) has been used to study the low temperature oxidation of coal. Specifically, SIMS imaging has been used to study the surface distribution of16O−and18O−after mild oxidation in18O2and to correlate the results with the organic and inorganic regions on the coal. In addition, coal surfaces have been treated with Tollens' reagent and the resulting silver deposition has been used as a probe for specific reactive oxygen functional groups. The results suggest the presence of surface peroxides, as well as an intimate association of reactive oxygen with the mineral apatite.