Membrane technology has become an essential tool in many industrial processes in which the separation or fractionation of various species is necessary to obtain or recover high value-added products. In these processes, the synthetic membranes usually play a filter role, being characterized by the size of the pores present in it, which delimit the size of the molecules to be separated.

It is therefore necessary to have a precise knowledge of the characteristic size of said pores. In this book, the main techniques that can be used to determine the mean pore size and the pore size distribution of a synthetic membrane are analyzed and discussed, from the point of view of their theoretical basis, with special attention to equipment that should be used for each technique, as well as reviewing their advantages and disadvantages. Through this text, the researcher or responsible of the quality-control at membrane manufacturing companies will be able to know decide properly which of the porosimetric techniques is more adequate for the knowledge that needs to be obtained from their filters.