The MMRRC is the nation’s premier national public repository system for mutant mice. Funded by the NIH continuously since 1999, the MMRRC archives and distributes scientifically valuable spontaneous and induced mutant mouse strains and ES cell lines for use by the biomedical research community. The MMRRC consists of a national network of breeding and distribution repositories and an Informatics Coordination and Service Center located at 4 major academic centers across the nation. The MMRRC is committed to upholding the highest standards of experimental design and quality control to optimize the reproducibility of research studies using mutant mice.