SUMMARY The secretion of dehydroepiandrosterone (DHA) and its sulphate (DHAS) was examined by measuring their concentrations in adrenal venous, gonadal venous, and peripheral venous plasma. Both steroids were secreted by the adrenal cortex and the rate of DHA secretion was higher than that of DHAS in seven out of eight subjects. Adrenocorticotrophin (ACTH) caused an increase in DHA and DHAS secretion by 15–30 min after administration. When ACTH was infused for 8 h, peripheral DHA concentrations increased at 2 h and decreased subsequently in five out of eight subjects suggesting depletion of substrate or cofactors for this biosynthetic pathway. Gonadal secretion of DHA was present in each subject (eight women and two men) but DHAS secretion could not be demonstrated. Exogenous human chorionic gonadotrophin (HCG) caused an increase in plasma DHA. Examination of the diurnal variation of plasma DHA concentrations revealed a 40% decrease from 08.00 to 20.00 h.