Affinity chromatography, with its exquisite specificity, is based upon molecular recognition. It is a powerful tool for the purification of biomolecules. In recent years, numerous new applications and modified techniques have been derived from gro- specific interactions and biological recognition principles. An up-to-date review of the past, current, and future applications of affinity chromatography has been presented in the introductory chapter by Meir Wilchek and Irwin Chaiken. Though many of these new applications and techniques are well documented in the literature, it is often difficult to find methods that are written with the intent of helping new practitioners of affinity chromatography. This volume on Affinity Chromatography: Methods and Protocols is intended for the novice, as well as for - perts in the field. The protocols are written by experts who have developed and/or successfully employed these methods in their laboratories. Each chapter describes a specific technique, and since the book is intended to help the beginner, each technique is described simply and clearly, making sure that all relevant steps are included, assuming no previous knowledge. Each chapter contains an introduction describing the principles involved, followed by a Materials and Methods section, which lays the groundwork for the reader to conduct experiments step-by-step, in an orderly fashion. The following Notes section, which describes many of the problems that can occur, makes suggestions for overcoming them, and provides alternate procedures. These are precisely the sort of important, practical details that never seem to appear in the published literature.