Abstract N- Acetyl- l-aspartic acid (NA-Asp), N- acetyl-α- l-aspartyl-L-glutamic acid (NA-Asp-Glu) and β-citryl- l-glutamic acid (β-CG), which are known to occur in the brain, have been isolated from human urine. Their identities were proved by comparing them with synthetic NA-Asp, NA-Asp-Glu and β-CG using electrophoretic and Chromatographie methods and by acid hydrolysis. A method was developed for the quantitation of NA-Asp, NA-Asp-Glu and β-CG in human urine. It consists of ion-exchange chromatography followed by gas-chromatographic analysis. The amounts of urinary excretion of NA-Asp, NA-Asp-Glu and ν-CG were 41.2 ± 10.1 ( n = 27), 20.8 ± 9.6 ( n = 27) and 30.2 ± 13.2 ( n = 21) μmol/g creatinine in adult males, and 62.2 ±16.3 ( n = 27), 24.0 ±8.2 ( n = 27) and 40.5 ± 21.1 ( n = 24) μmol/g creatinine in adult females, respectively.