This is an introduction to the methods and applications of polymerase chain reaction (PCR) technology, a technology developed by Erlich's group at Cetus and Cetus, and is expected to be used in all biology laboratories worldwide within the next few years.Part 1 Introduction to the PCR: history of PCR development; description of the PCR method - basic principles and properties of the PCR; thermostable DNA polymerases; automation; sample preparation. Part 2 Research applications - brief overview: direct sequencing using PCR; preparation of specific DNA fragments using PCR; detection of gene expression; genetic mapping using PCR amplification of individual gametes. Part 3 Diagnostic applications - brief overview: detection of pathogens; diagnosis of monogenic genetic diseases; HLA DNA typing and disease susceptibility; forensic applications; detection of activated oncogenes; future developments and applications.