A 2-year-old girl with virilization had an adrenal tumor that produced testosterone with little evidence of excessive urinary androgen excretion. Plasma testosterone concentration was 407 ng/dL and urinary 17-ketosteroid (17KS) levels were 3 and 2 mg/day. Excretion of 17KS decreased to 1.8 mg/day after suppression of dexamethasone therapy, but urinary 17-hydroxycorticosteroid excretion did not change from 1.0 to 0.7 mg/day after administration of dexamethasone. She had a blunted response to administration of metyrapone and insulin and a small diurnal variation in cortisol concentration suggesting suppression of corticotropin secretion, even though the plasma cortisol concentration was in the normal range and there were no clinical signs of cortisol excess. High-performance liquid chromatography was used to analyze the steroid content of tumor tissue. Those portions of the tumor that were rich in steroids contained predominantly testosterone.