A number of text books are commercially available on the polymerase chain reaction (PCR), its types and applications but these books are far away from the approach of the students due to their high cost. The purpose of this book is to provide the authentic material to the students in affordable price. A very simple language is used in the book so easy to understand. This book covers the basic principle, reagents, equipment and methodology of the PCR. Furthermore this book also covers optimization of various parameters for the improvement of the PCR product. Different types of PCR and its applications in various fields have been discussed in detail. This book is an easy way to study the most of aspects of PCR. At the end I am thankful to the contributing authors for sparing their time and writing a chapter on a specific topic for this book.