'It has become increasingly clear that the surfaces of all kinds of atmospherically abundant particles- for instance, ice, soot, sulfuric acid, and salt- catalyze and promote reactions that perturb the composition of the atmosphere. While there is a growing body of evidence that suggests that reactions on mineral aerosol may play an important role in the troposphere, there is very little understanding of what chemistry occurs on the surface of these particles. The focus of this talk is on recent laboratory studies of surface reactions of trace atmospheric gases on oxide and carbonate particles. These particles are used as laboratory surrogates for mineral aerosol. Spectroscopic and kinetic measurements are made of potentially important surface reactions in the atmosphere so as to gain insight into the mechanism of reactions of trace atmospheric gases on mineral aerosol and to quantify the rates of these reactions. The kinetic data are used as input into atmospheric chemistry models in order to assess the importance of these surface reactions in the troposphere.