AbstractThe1H NMR spectrum of the putative neurotransmitter dipeptideN‐acetylaspartylglutamate (NAAG) is described, along with its identification in acid extracts of tissues of the central and peripheral nervous systems of the rat. TheN‐acetyl methyl resonance of NAAG (2.058 ppm) is close to that ofN‐acetylaspartate (NAA, 2.022 ppm), a prominent signal in1H NMR spectra of the brain. The tissue concentration of NAAG is such that resonances of NAAG do not contribute greatly to1H NMR spectra of the brain, except in studies of the brain stem or thalamus. In the spinal cord and peripheral nerves the level of NAAG is similar to that of NAA, and NAAG is a major metabolite contributing to the1H NMR spectrum. The implications of these observations for1H NMR spectrain vivoare disc