In situ hybridization is used to reveal the location of specific nucleic acids sequences on chromosomes or in tissues, a crucial step for understanding the organization, regulation and function of genes. This popular, hands-on guide has been thoroughly updated to cover the key techniques currently in use. These include in situ hybridization to mRNA with oligonucleotide and RNA probes (both radio labelled and hapten labelled); analysis with light and electron microscopes; whole mount in situ hybridization; double detection of RNAs and RNA plus protein; and fluorescent in situ hybridization to detect chromosomal sequences. The protocols are complemented by advice on strategies for successful results, descriptions of the theoretical basis for the methods, and important new developments in gene expression databases. Collecting reliable and well-tested techniques, this volume will prove an essential tool for a wide range of biomedical researchers.