The University of California, Davis (UCD) proposes to build upon existing expertise, technology, and facilities of its own Mouse Biology Program to establish a Mutant Mouse Regional Resource Center (MMRRC) as part of a regional center of excellence in Mouse Biology. The UCD-MMRRC will coordinate its activities with the national Coordinating Committee and establish efficient and responsive computer linkage with the Informatics Coordinating Center. UCD will offer its existing broad range of expertise to respond flexibly to the varied needs of mutant mice and their scientific constituency. This flexible approach is required for effective importation, rederivation, cryopreservation, maintenance, breeding, distribution, and revitalization from the cryopreserved state. These functions will be enhanced by a consulting arrangement with scientists at The Jackson Laboratory, and via an informal partnership with Harlan Sprague Dawley, Inc. for efficient distribution of mice created by the UCD MMRRC. UCD research programs in mouse sperm cryopreservation, with collaboration of scientists at the University of Hawaii, miniaturized magnetic resonance imaging, and an integrative comprehensive network of phenotyping expertise are offered to enhance the MMRRC and the national MMRRC network. The MMRRC will support programs in phenotyping and development of an interactive internet site, termed The Visible Mouse, which will make data on normal anatomy and pathology of mutant mice accessible to the national scientific community.