Separation processes in biotechnology are of increasing industrial importance since they entail the major costs of bioprocessing especially when high purity is required. Chromatography and membranes are two of the most important technologies used for direct treatment of fermentation broths as well as for high resolution steps in product purification. The theoretical foundations of chromatographic and membrane processes are well understood for the case of small molecules. Nevertheless there is a need to adapt and further develop that knowledge to the processing of large biological molecules. This is being achieved with the contribution of other areas like molecular biology and materials science. The objective of this NATO Advanced Study Institute is to present an updated treatment of the fundamentals of chromatographic and membrane processes with special relevance in bioprocessing.This volume collects the lectures presented at this Institute. The lectures are arranged in five chapters. Chapter I deals with chromatographic processes covering topics like equilibrium, kinetics and contacting devices. Membrane processes and some applications in biotechnology are treated in chapter 2. Chapter 3 is devoted to affinity chromatographic and membrane processes. Chapter 4 considers the current developments on chromatographic supports and membranes both from the constitutive materials and form points of view. Scale-up, optimization and reaction/separation integration are the topics covered in chapter 5. We are very grateful to all lecturers and participants that made possible this Institute. Financial support from NATO Scientific Affairs Division, INIC, JNICT, FLAD, University of Ac;ores and DRT Ac;ores is gratefully acknowledged.