The first-morning urine and random spot urine at noon and night for 3 consecutive days were collected from young healthy volunteers (n=20, age 21–25, male/female = 1/1), and analyzed by HPLC. The concentrations were 34 ± 9 µM. There was a strong correlation between the urinary concentration of l-β-EHAsn and creatinine (r = 0.91) (A), and whose values were 4.5 ± 0.5 (nmol l-β-EHAsn/mg creatinine). No correlations between urinary excretion of l-Asn and creatinine were observed (B).