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The origin, the classification and the effect on catalytic performance of pore texture of heterogeneous catalysts are briefly examined. The techniques and the methods suitable for the determination of related properties (surface area, pore volume and pore size distribution) are reviewed. Particular attention is paid to the most widely used ones: vapour adsorption at low temperature, mercury porosimetry, incipient wetness impregnation and picnometry. Advantages, disadvantages and applicability of each method to different pore textures are pointed out. The best choice of a group of methods, allowing a complete characterization of catalysts, is proposed.

The most remarkable difference between catalysis during the 50s and 60s and nowadays is the remarkable development of characterization techniques. Various factors contributed to that growth: (i) need of having a better control on the catalyst in order to meet the requirements for further optimization of processes already in operation and/or for realization of new processes; (ii) appearance of new classes of solids with catalytic properties and peculiar characteristics (zeolites, zeolite-like materials, oxides with controlled porosity, very high pore volume silica, superacids, etc.); (iii) technology and computer development have placed on the market more powerful and friendly to use versions of known techniques (FT-IR, FT-Raman, calorimeter, etc.) or new techniques, often initially developed for other sectors use (XPS, EXAFS, SIMS, ISS, EPMA, etc.). To realize how large is the growth of the characterization influence in the development of catalysts it is enough to look at scientific magazines and catalysis congresses proceedings. Because of the tremendous variety of disposable techniques it is impossible to review all of them in few pages. So we have to decide what techniques to describe and what to treat deeply. The choice has been done on the basis of: (i) applicability to real catalysts (so spectroscopies on single crystals like LEED, UPS, etc. were rejected); (ii) easy access, either in cost and/or in necessary facilities (however also techniques both expensive like XPS, NMR, TEM and of difficult access like EXAFS, requiring synchrotron radiation, will be reported because of their importance); (iii) applicability to many different systems (then little space will be devoted to Miissbauer and PAS, much more to N, adsorption, IR spectroscopy and temperature programmed techniques, etc.); (iv) informative content, or capacity to give a manifold information (multipurpose techniques like IR spectroscopy are preferred). On the whole 35 techniques, i.e. a number enough to face adequately nearly all the problems of daily practice, are described; on a few other (about 20) a short description is given. For all of them an adequate bibliography useful for a first deepening will be given. Techniques have been grouped on the basis Of: 1. morphology and physical characteristics, 2. surface characteristics

While the most frequently used characterization techniques in catalysis have been described in the first part of this paper, in this part the application of the techniques to the solution of practical problems is described.