Serum concentrations of the adrenal androgen, dehydroepiandrosterone sulfate, were measured by radioimmunoassay in normal infants and children, in sick premature and full-term newborn infants, and in patients undergoing evaluation of the hypothalamic-pituitary-gonadal and -adrenal systems. Premature infants had significantly greater (p less than 0.001) levels of DHAS (263 +/- 40)[SE]migrong/dl) than did full-term infants (58.9 +/- 5.2) during the first ten days of life; further increments occurred in stressed "sick" infants. A gradual age- and maturity-related rise in serum concentrations of DHAS was observed during childhood with the earliest increase occurring prior to the onset of pubertal production of gonadal steroids. Serum levels of DHAS rose following administration of ACTH and were increased in patients with congenital adrenal hyperplasia, in whom rapid decrements followed treatment with dexamethasone. hCG or LH-RH treatment did not alter DHAS concentrations. These data suggest that direct secretion of DHAS by the adrenal gland and/or peripheral sulfation of DHA, rather than gonadal secretion, accounts for the majority of DHAS production. The involvement of adrenal androgens in the pubertal maturation of the reproductive endocrine system thus may be evaluated by quantitation of serum DHAS.