In order to determine the source of androgens in precocious adrenarche, serum androgens were determined in 8 girls with precocious adrenarche and 5 agonadal children in adrenarche under conditions of adrenal and gonadal stimulation and suppression. All androgens increased with ACTH stimulation in both groups. Stimulability of serum androgens in girls with precocious adrenarche with ACTH was more consistent than in 13 prepubertal children. Human chorionic gonadotropin administration increased serum Δ4 androstenedionetestosterone and dihydrotestosterone in the girls with precocious adrenarche but not in the agonadal children, demonstrating the failure of HCG to stimulate adrenals. Dexamethasone suppression decreased levels of all androgens in both groups, whereas Norlutin or Ovral produced variable changes. These studies support the adrenal origin of androgens in precocious adrenarche and the lack of ovarian contributions in this condition.