Urinary 17-hydroxycorticosteroids (17-OHCS) and cortisol have been determined in children with normal and abnormal adrenocortical function and a sample of adults. Mean values (±SD) for mg 17-OHCS/gm creatinine were 4.7 ± 1.4 in 30 normal children, 4.1 ± 2.2 in 4 obese children and 4.4 ± 1.7 in 11 adults. Mean values (± S D) for μg cortisol/g creatinine were 75 ± 18, 54 ± 17 and 68 ± 15, respectively. Neither 17-OHCS nor cortisol excretion was significantly different between the groups. Mean values (± SD) of 10.4 ± 3.1 mg 17-OHCS/g creatinine and 234 ± 94 ng cortisol/g creatinine were found in S children subjected to stress and values decreased following dexamethasone administration to 2 of the group. In a child and an adult with Cushing's syndrome, 17-OHCS were 17.7–37.7 mg/g creatinine and cortisol, 206–1313 M-g/g creatinine. In a child with Addison's Disease, 17-OHCS were 0.9–2.2 mg/g creatinine and cortisol, 7–9 μg/g creatinine. Results of the study suggest that urinary excretion of 17-OHCS and cortisol is comparable in adults and children and that both determinations are useful in the diagnosis of adrenocortical disorders in childhood.