Serum testosterone assays were performed on 16 hirsute women and 3 nonhirsute volunteer control patients by obtaining adrenal, ovarian, and peripheral venous blood samples from the femoral vein by a percutaneous catheter approach. Eight demonstrated elevated androgen secretion of adrenal origin (including 1 virilized patient), 5 had combined adrenal and ovarian hypersecretion, and 2 were felt to have elevated serum testosterone of peripheral origin, while 1 hirsute female was found to have no increase in androgen secretion. This method of testing the source of excess androgens is relatively simple, appears to be associated with no morbidity, and does not require lengthy, potentially inaccurate suppression and stimulation studies. Testosterone assays performed by commercial laboratories are available to gynecologists in private practice, circumventing the need of complex research laboratory facilities. Follow-up studies are in progress to determine the accuracy of the functional disorder suggested by this procedure.