The Mutant Mouse Resource and Research Center (MMRRC) is the nation’s primary mutant mouse archive and distribution repository system. The MMRRC was established by the NIH to ensure the preservation, dissemination, and development of valuable mutant mouse lines and data generated by research scientists. The MMRRC is a consortium of four Centers, each hosting an archive and distribution repository, and an Informatics Coordination and Service Center (ICSC) within a trans-national network regionally distributed across the United States. The Centers collectively serve the needs of the nation’s biomedical research community, ensuring access to and optimizing utilization of transgenic, knockout and other genetically engineered mutant mice and related biomaterials, services, and new technologies. The Centers import, verify, maintain, and distribute mice, gene-targeted embryonic stem (ES) cells, and germplasm of genetically unique, scientifically valuable mice. Centers also provide services and procedures to assist investigators using genetically-altered mice for research. Finally, Centers conduct resource-related research and develops and refines technologies that further develop mutant mouse lines and that capitalize on the power of mouse genetics for biomedical research. By depositing their mutant mice in repositories at the Centers, NIH-funded investigators fulfill their obligation under the NIH Sharing Policy. In return, each of the Centers strives to preserve, protect, quality control, and provide these models for the benefit of research scientists and investigators across the nation and the globe. The ultimate goal of the MMRRC is to facilitate research by identifying, acquiring, evaluating, characterizing, cryopreserving, and distributing mutant mouse strains to qualified biomedical investigators. The MMRRC ensures that valuable mutant mouse lines are available equitably across the biomedical research community, thereby accelerating the pace of research discovery using genetically-altered mice. With input from an External Advisory Committee (EAC) of experts, the longterm sustainability and relevance of the MMRRC to biomedical research is assured.