The polymerase chain reaction (PCR) makes possible rapid generation of a very large number of copies of a specific region of DNA. This enables the typing of quantities of DNA as small as a single molecule. PCR has led to the development of laboratory experiments which provide new approaches to many classic problems in genetics, such as estimation of linkage, marker ordering and genetic disease diagnosis. We describe some of these experiments and the statistical techniques that have been used to design them and to analyze the data they produce.