Comparative results of the suppression-stimulation test by dexamethasone and chorionic gonadotropin, chromatographic separation of 17-ketosteroids, and plasma testosterone levels in the ovarian and adrenal veins, in cases of virilism in women. Thirteen patients with hirsutism and virilization were investigated as follows: 1. measurement of plasma testosterone (T) levels by radioimmunoassay (RIA) during suppression-stimulation tests by the administration of Dexamethasone (DXM) and chorionic Gonadotropin (HCG). 2. chromatographic determination of urinary 17-ketosteroids, pregnanediol (P2), and pregnanetriol (P3). An attempt was made to classify virilism as "ovarian" or "adrenal" based on the results of 1. and 2. 3. bilateral ovarian and adrenal venous catheterization through the femoral vein to measure T (RIA) levels. 4. laparotomy with bilateral wedge resections of the ovaries for therapeutic and biopsy purposes. Surgical catheterization of the ovarian veins was carried out during the operation. The results of these tests show that: a) the dynamic DXM-HCG test can be used to separate those cases in which the ovary is not involved in T formation from those in which, apparently, it is involved. b) chromatographic determination of urinary steroids has no aetiological value, as the variations in the different fractions are not significant. c) in all patients, the principal source of T is the adrenals and not the ovaries, even when there is an increase in T in the ovarian efferent blood vessels.