A brief description of the structure and ion exchange behavior of several classes of inorganic ion exchangers is presented. These include hydrous oxides, layered compounds, and exchangers with tunnel structures. Some salient features of the thermodynamics of ion exchange with layered compounds is then described. Increasing use of inorganic exchangers in environmental chemistry and other areas of technological importance is suggested on the basis of their high selectivities and resistance to destructive or harsh media.