The concept underlying this book has not changed from the first edition; it is to providean introductory text that is hopefully useful to undergraduate students, graduate studentsand other scientists who want to understand and use PCR for experimental purposes.Although applications of PCR are provided these do not represent a comprehensivecatalogue of all possible PCR applications, but serve to indicate the types of applicationpossible. The main purpose of this new edition of PCR, as for the first edition, is toprovide information on the fundamental principles of the reactions occurring in a PCRtube. Understanding these basic features is essential to fully capitalize upon and adapt thepower of PCR for a specific application. This means that the structure of the book remainssimilar to that of the first edition. The first six Chapters discuss the fundamental aspectsof performing PCR and of analyzing and cloning the products. All these Chapters havebeen updated and additional aspects added where appropriate. In some Sections there isdiscussion of particular enzymes or instruments. However, clearly suppliers are continuallychanging their formulations or designs and so these are provided only to indicate thedifferent types. We recommend checking manufacturers’ literature for new and improvedsystems, particularly when it comes to investing in the purchase of a new PCR instru-ment. In terms of the applications, a new Chapter has been written on real-time PCR,which represents a very sensitive and reliable method for providing information about therelative concentrations of starting template molecules, such as mRNA or genomic genes.The remaining Chapters have been updated and Protocols have been rationalized to retainthose that are likely to be the most useful. We have also removed the list of web addressesof various reagent suppliers. Such lists can quickly become outdated and it is simpler forthe reader to identify the up to date website from a web search engine. We hope that thisbook will provide the basic information required to get scientists started with PCR experi-ments either to use it simply as a routine tool, or as a starting point for developing newand innovative processes.