This request for $390,894.19 from the University of California, Davis is intended to support the purchase and installation of 20 OptiMICE passively-ventilated mouse racks and cages necessary for the care and maintenance of a growing number of genetically-altered mouse lines. These cages are to be used to house mice for 26 investigators: 19 conducting 27 active research projects (25 PHS- funded, 2 non-PHS funded) totaling $8,873,746 annual direct costs and 7 with 7 pending research grants (6 PHS-funded, 1 non PHS-funded), a 25% increase, totaling $2,648,652 annual direct costs. While all of these grants will benefit from the use of these cages, 2 of the active NIH grants, the U42 RR14905-09 Mutant Mouse Regional Resource Center (MMRRC) and the U42 RR024244 Knockout Mouse Project (KOMP) Repository, will be the major users. In anticipation of an award, UC Davis has provided a dedicated, 20,000 ASF laboratory building, including a 6000 sq ft, 5-room mouse vivarium, for mouse-related research and resource activity. After a recent $3million renovation that included upgrades and an expansion of its electrical, plumbing, and HVAC capacity, the building was sized to accommodate 40 OptiMICE systems in the vivarium. However, today the vivarium holds only 20 racks and cages, representing just half of the total cage footprint, but that half is operating at 90% of capacity. The 20 racks and cages to be purchased by this G20 request will fill the remaining half of the total cage footprint, and thus enable the vivarium to meet the projected near-term demand for mouse housing. Because of a significant increase in the number of active grants requiring mouse housing, projections indicate that the growth in number of mutant mice will demand 90% of this total capacity within the next 5 years. UC Davis will also provide increase staffing and other support to ensure that the vivarium operates efficiently and effectively, and maintains AAALAC- accreditation.