The first edition of Protein Purification Protocols (1996), edited by Professor Shawn Doonan, rapidly became very successful. Professor Doonan achieved his aims of p- ducing a list of protocols that were invaluable to newcomers in protein purification and of significant benefit to established practitioners. Each chapter was written by an ex- rienced expert in the field. In the intervening time, a number of advances have w- ranted a second edition. However, in attempting to encompass the recent developments in several areas, the intention has been to expand on the original format, retaining the concepts that made the initial edition so successful. This is reflected in the structure of this second edition. I am indebted to Professor Doonan for his involvement in this new edition and the continuity that this brings. Each chapter that appeared in the original volume has been reviewed and updated to reflect advances and bring the topic into the 21st century. In many cases, this reflects new applications or new matrices available from vendors. Many of these have increased the performance and/or scope of the given method. Several new chapters have been introduced, including chapters on all the currently used protein fractionation and ch- matographic techniques. They introduce the theory and background for each method, providing lists of the equipment and reagents required for their successful execution, as well as a detailed description of how each is performed.