Non-conjugated catecholamines were measured in morning urine samples from 111 healthy, non-hospitalized subjects aged 8-18 y and in 16 hospitalized, healthy subjects aged 12 16 y. The catecholamines were extracted by cation exchange columns and alumina adsorption and quantitated with HPLC with electrochemical detection. The concentration of catecholamines was related both to the urinary creatinine concentration and to the collecting period and body surface area. Linear regression analysis was used to estimate continuous age-related reference centiles based upon the measurements from the 111 non-hospitalized subjects. The upper limits for the adrenaline/creatinine and noradrenaline/creatinine ratios were lower than in previous studies. The excretion of adrenaline and noradrenaline per hour and m2 body surface area was higher in the 16 hospitalized than in the 74 age-matched non-hospitalized subjects. The excretion of the catecholamines expressed per hour and m2 body surface area and expressed relative to creatinine excretion, decreased with increasing age, and the excretion of adrenaline and noradrenaline per hour and m2 body surface area was higher in boys than in girls. In conclusion, standardization of urine sampling leads to more narrow ranges for urinary adrenaline and noradrenaline excretion in healthy children and adolescents.