The Indiana University School of Medicine (IUSM) has experienced a substantial increase in the use of genetically engineered mice (GEM) in recent years. These animals are critical for the School's major research focuses, including studies of cancer, diabetes, and other health problems of importance in the USA. Our rapid growth in the use of GEM has created a need for more efficient and greater housing capacity in the Laboratory Animal Resource Center (LARC). In 2009, we utilized institutional resources to build Walther Hall, a research building containing an 18,000 square foot rodent housing facility. This facility was designed to house a maximum of 12,900 cages of mice. We were able to purchase individually ventilated caging systems representing approximately 10,000 cages of mice when the building opened. Funds from this grant proposal will be used to purchase 14 Modular Animal Caging Systems (MACS(R), Alternative Design Manufacturing &Supply, Inc.) with associated automatic watering system (Edstrom Industries, Inc) capabilities for our Walther Hall animal facility to add 2,240 cages, increasing the housing capacity of this animal facility. This represents a 22% increase in the housing capacity for the Walther Hall animal facility. The purchase of these additional individually ventilated caging systems will allow us to meet our specific aims of increasing the available housing capacity required by our principal investigators, protecting the health and well-being of the mice, providing personnel protection for the employees working in the animal facilities, and increasing the operational efficiencies of the animal facility.