The polymerase chain reaction (PCR) – an in Vitro techniques for producing large amounts of a specific DNA fragment – has rapidly become established as one of the most important, impressive and fascinating methods of molecular biology as well as clinical diagnostics. In the seven years since’the technique was published, it has had a major impact on medical research. However, as there are still problems in instruments, standardized protocols for diagnostic applications and unsolved difficulties to avoid cross-contaminations on the one hand and on the other hand the even present question of how to interpret the biological value of a PCR- result, most clinicians prefer to further wait until these topics are clarified. It is the aim of this book to give the reader lab-proven protocols from experienced scientists as well as a general introduction to alternative DNA-amplification procedures and their possible usage such as the NASBA or LCR. This book is divided into four major parts to provide a theoretical (first and second section) and a practical framework for a better understanding of the new technology. In the first part we provide an up-to-date summary of basic problems in this rapidly evolving field. We demonstrate, for example how to use fixed tissue materials and how to quantify PCR products as well as how to prepare nucleic acids in a safe, convenient and proper way, or even how to sequence directly PCR products for the analysis of the DNA structure.