In situ hybridization is used to reveal the location of specific nucleic acids sequences on chromosomes or in tissues. Visualization of the location of genes on chromosomes or of specific mRNAs or viruses in tissues is crucial for understanding the organization, regulation, and function ofgenes. It is a therefore a core technique in all areas of biomedical research. In Situ Hybridization: A Practical Approach 2/e is the second edition of one of the most successful Practical Approach books, published in 1992. Since the first edition was published, a number of important technicaladvances have been made. The new edition has been thoroughly updated to contain protocols detailing the major techniques of in situ hybridization currently in use: in situ hybridization to mRNA with oligonucleotide and RNA probes (radiolabelled and hapten labelled); analysis using light and electronmicroscopes; 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 of in situhybridization and important new developments in gene expression databases. The procedures described are widely applicable to many systems. The use of in situ hybridization in PCR is covered in a separate volume: Herrington and O'Leary (Eds) PCR 3 - PCR in situ hybridization: A Practical Approach(OUP, 1997). All the authors have extensive practical experience of establishing reliable techniques of in situ hybridization. This book will be useful to all researchers at all levels who use in situ hybridization.