The peripheral levels of 17-hydroxypregnenolone (17Δ5(P), progesterone (P), 17-hydroxyprogesterone (17P), testosterone (T), 5α-dihydrolestosterone (DHT), androstenedione (A), androst-5-ene-3α,17α-diol (Δ5diol), dehydroepiandrostcrone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), estradiol-17β (E2), and cortisol (F) were measured in peripheral and right adrenal venous blood of an amenorrheic patient with a right virilizing adrenal adenoma. Urinary 17-ketosteroids were markedly elevated and were not suppressed on a low dose of dexamethasone (Dex) for 7 days. Peripheral T level was 1.2 ng/ml and DHEA-S was 13,500 ng/ml. Calculations of the ratios of adrenal venous gradients for Δ5 and Δ4 steroids suggest that the predominant pathway of steroid secretion used by the tumor was as follows: pregnenolone (Δ5P) 17Δ5P DHEA A T. Following removal of the adenoma, T returned to normal levels but DHEA-S was still above normal at 4100 ng/ml. The patient became eumenorrheic with marked improvement of her hirsutism and virilization.