To better understand pathological aging, we must first have a thorough understanding of changes that occur in the brain during healthy aging. This project employs Magnetic Resonance Spectroscopy to characterize longitudinal changes in the neurochemical profile of healthy Fischer 344 rats. In addition to the commonly reported metabolites, nine macromolecular resonances were included in the basis set and quantified, based on parameterization of a group-averaged metabolite-nulled spectrum. For the first time, longitudinal age-related changes in metabolites and individual macromolecules were simultaneously characterized in the Fischer rat. Sex-specific differences were also identified in metabolites and macromolecules.