The Transgenic and Chimeric Mouse Facility has been continuously funded by the NCI CCSG since 1989. Nancy Cooke, MD, Professor of Medicine and Genetics, has provided leadership to this Shared Resource since 1993. Dr. Cooke is an experienced investigator with considerable expertise in transgenic and gene knock-out experimentation. Co-Facility Director Stephen Liebhaber, MD, Professor of Genetics and Medicine, has worked with Dr. Cooke since the Facility was first planned and has contributed significantly to the initial establishment and subsequent expansion of many of its services. An experienced technical team under Jean Richa, PhD, provides expertise in a range of transgenic technologies, enabling the Facility to regularly introduce new and improved services. Among the services provided by the Transgenic and Chimeric Mouse Facility are: generation of transgenic mice via microinjections of DNA into fertilized oocyte; generation of chimeric mice via injection of embryonic stem cells into blastocysts; embryo rederivation; embryo and sperm cryopreservation; in vitro fertilization; centralized and monitored cryopreservation storage; and maintenance of useful animal stocks including recombination-activation gene expression lines. The Core has intracytoplasmic sperm injection capability to complement the in vitro fertilization service. Newly developed services during the current funding period were computer generated logs for ordering, online tracking of services for investigators, acquisition of a centralized and dedicated cryopreservation facility with on-line catalog and tracking of lines under cryostorage, genotyping of tail DNAs, and integration of mouse ES microinjection service with centralized gene knock-out services. Over 20 ACC members have used the facility in the last year. ACC member usage is 41% of the total core usage. CCSG support represents 21% of the proposed core budget with the remaining funding coming from charge backs and other grants/contracts. Additional institutional support is provided in the form of funding for equipment maintenance and the new cryopreservation storage facility.