The present proposal requests funding for the purchase of a gas chromatograph mass spectrometer (GC/MS), which is essential to current and future research programs in human and animal nutrition and metabolism at the Indiana University School of Medicine. The instrument requested is a critical component of the Mass Spectrometry Core Laboratory, which has supported NIH funded investigators conducting stable isotopic tracer studies since 1989. The current 13-year-old instrument has not been manufactured in many years, and now the company has discontinued all service support on this instrument. Replacement for this GC/MS is critical to 3 currently funded R01 projects and 1 K23 grant, and to the Mass Spectrometry Core Laboratory's ability to provide analyses for additional and future research. In particular, the Core Laboratory has supported and continues to support the clinical research training of new investigators using stable isotope techniques. Fostering the development of new clinical researchers is an important goal of the NIH and the Indiana University School of Medicine, and new instrumentation will allow this to continue. Finally, a new and more efficient instrument will facilitate the ability of other investigators across the campus to use the laboratory.