There is a great deal of interest in the general subject of porous inorganic materials in regard to their use as sorbents or catalysts. The solids may be microporous, mesoporous, or macroporous. Often there is a range of pore sizes within any given solid, and so there is special interest in the synthesis, characterization and application of solids having well-defined pores. The first part of this text deals with the theory and practice of the measurement of pore-size distributions. Part 2 goes into porous crystalline materials. The zeolites are, by definition, microporous, but it is important to understand the mechanisms whereby such crystalline porous materials are formed, so as to suggest methods for the synthesis of mesoporous materials. Pillared layered solids are investigated in Part 3. There are clear indications that the current generation of microporous materials may be developed to give PLS which combine micro and mesoporosity, while a totally mesoporous solid may not be far off. Part 4 covers sol-gel methods, where important new developments mean that oxides can be produced with high purity and with well-defined pore sizes. Methods of characterizing the materials are also studied, with solid state NMR (including 27AI-NMR), X-ray and neutron scattering, pulsed ESR, and electrokinetic potential measurements being discussed in Part 5. Finally, applications are discussed in Part 6.