This is a completely revised and expanded edition of the Guidebook to Biochemistry. Every chapter has been reviewed and brought up to date. A new chapter, on the cell and membrane transport, has been included, and the single chapter on regulation in the previous edition has been greatly enlarged and divided into two chapters. Other topics that have received particular attention in this edition include lipids, cell membranes and the biochemical action of hormones. The chapter on genetics has been revised to take account of recent studies of the genetic organization of higher organisms, and a section on genetic engineering has been included. In making these changes the authors have taken care to adhere to the concept of the 'Guidebook' introduced by Kenneth Harrison and maintained by them in the 1971 edition: to 'introduce the reader to the important features of the subject by exemplifying and discussing crucial biochemical concepts'. For this reason they have been careful to restrict the increase in the total length of the book compared with the 1971 edition.