Free amino acids were determined quantitatively by ion exchange column chromatography in 24 h urine of 354 (male = 187, female = 167) "healthy" infants, children and adolescents. Urine was deproteinised by 5% sulphosalicylic acid (1:1, v/v). The results - 95% confidence range - are presented age-dependent (groups: up to 1 month, 1-24 months, 2-6 years, 6-10 years, 10-14 years) and sex-dependent in table 3 and 4.