Overview: Gene Knockouts, Paul J. Hertzog and Ismail Kola. Isolation and Maintenance of Primate Embryonic Stem Cells, Vivienne S. Marshall, Michelle A. Waknitz, and James A. Thomson. Gene Targeting in ES Cells, Thomas M. DeChiara. Manipulating Mouse Embryonic Stem Cells, Lino Tessarollo. Gene Targeting in a Centralized Facility, Louise D. Barnett and Frank Kontgen. The LoxP/CRE System and Genome Modification, Trevor J. Wilson and Ismail Kola. Creation and Use of a Cre Recombinase Transgenic Database, Andras Nagy and Lynn Mar. Choice of Mouse Strains for Gene Targeting, Mireille H. Lahoud, Trevor J. Wilson, and Paul J. Hertzog. Isolation, Microinjection, and Transfer of Mouse Blastocysts, Angelika Bonin, Susan W. Reid, and Lino Tessarollo. Aggregation Chimeras: Combining ES Cells, Diploid and Tetraploid Embryos, Mika Tanaka, Anna-Katerina Hadjantonakis, and Andras Nagy. How to Study Pathologic Phenotypes of Knockout Mice, Roderick T. Bronson. Analysis of Hematopoietic Phenotypes in Knockout Mouse Models, Ivan Bertoncello and Brenda Williams. Isolation of Embryonic Fibroblasts and Their Use in the In Vitro Characterization of Gene Function, Paul J. Hertzog. Influence of Genetic Background on Knockout Mouse Phenotypes, L. Philip Sanford, Suhas Kallapur, Ilona Ormsby, and Thomas Doetschman. Lineage Allocation During Early Embryogenesis: Mapping of the Neural Primordia and Application to the Analysis of Mouse Mutants, Gabriel A. Quinlan, Bruce P. Davidson, and Patrick P. L. Tam. Generation of Double-Knockout Embryonic Stem Cells, Hein te Riele, Conny Brouwers, and Marleen Dekker. In Vitro Differentiation of Embryonic Stem Cells and Analysis of Cellular Phenotypes, Anna M. Wobus, Kaomei Guan, and Uta Pich. Embryonic Stem Cells in the Study of Hematopoiesis, Francesca Lazner, Ismail Kola, Elizabeth Stadler, and Andrew G. Elefanty. Interferon-Inducible ES Cell Expression Systems, Linda M. Whyatt and Peter D. Rathjen. Transgenic Studies in the Mouse: Improving the Technology Towards a Conditional Temporal and Spatial Approach, Sika Ristevski. In Vivo Libraries of Large Insert Transgenic Mice for Genetic Mapping, Desmond J. Smith. Epigenetic Effects on Transgene Expression, Emma Whitelaw, Heidi Sutherland, Margot Kearns, Hugh Morgan, Linda Weaving, and David Garrick. Positional-Candidate Cloning of Genes from Mouse Mutants, Karen B. Avraham. Genetically Engineered Mice: Husbandry and Resources, John J. Sharp, Carol C. Linder, and Larry E. Mobraaten. Embryo Cryopreservation for Transgenic Mouse Lines, Jillian M. Shaw and Magosaburo Kasai. Index.