Biophotonic imaging of small animals using bioluminescent and fluorescent probes has become a state-of-the-art technology for studying normal and disease processes in vivo and is providing powerful new approaches for studying tumor biology, infectious disease, and gene expression. This application requests funds for a Xenogen MS 200 biophotonic imaging system to support a wide range of research being carried out at Tufts University Schools of Medicine and Dental Medicine and the Tufts-New England Medical Center in Boston. A core group of 12 well-funded NIH investigators will be the primary users of the instrument and will account for approximately 79% of its use. A small animal imaging facility will be established to house the imager. Establishment of the facility is strongly supported by the Chairman of the Department of Physiology, who has offered laboratory space for the facility and support for administration of the grant, by the Dean of the Medical School, who will provide funds for renovation of the laboratory space, and by the Vice President of Research at Tufts-New England Medical Center who has offered funds for maintenance of the instrument. The facility will be directed by the PI and the instrument will be operated and managed on a day-to-day basis by a full time research associate who will also train new users. An advisory committee consisting of the PI, and representatives from Tufts-New England Medical Center, the Division of Laboratory Animal Medicine and the Department of Physiology will oversee use of the MS 200 system and develop policies for use and equitable sharing of the instrument. At present, the PI has an MS imager on loan from Xenogen that is being shared by several of the major users. However, this instrument will have to be returned to Xenogen and no other suitable imager is available for use at Tufts University or the Tufts-New England Medical Center. The presence of the new MS 200 imaging system and imaging facility will greatly enhance the research carried out on the Tufts University Health Sciences Campus in Boston.