An 11-year-old premenarchial girl who demonstrated the clinical and biochemical abnormalities of the Stein-Leventhal syndrome is reported. Although the concentration of total circulating testosterone was within normal limits, levels of free testosterone and testosterone-estradiol-binding globulin (12.9 to 22.7 pg/ml and 7.9 to 11 X 10(-9) moles/liter, respectively) were markedly different from those of prepubertal girls (1.1 +/- 0.9 pg/ml and 102 +/- 27 X 10%-9) moles/liter, mean +/- 1 SD) and normal women (4.3 +/- 1.2 pg/ml and 82 +/- 30 X 10(-9) moles/liter). Luteinizing hormone but not follicle-stimulating hormone concentrations were increased. In the absence of abnormal adrenal steroid excretion or response to dexamethasone suppression and with a clear biochemical response to oral contraceptives (decreased levels of luteinizing hormone and free testosterone and increased concentrations of testosterone-estradiol-binding globulin), this patient closely resembles older individuals with the Stein-Leventhal syndrome. Therefore, the measurement of testosterone-estradiol-binding globulin and free testosterone may be useful in the laboratory evaluation of any adolescent girl in whom no other cause for hirsutism can be identified.