Hyperandrogenism in adolescent girls can be a troubling problem because of the difficulty in establishing a diagnosis and in prescribing appropriate therapy. Androgen excess in adolescent patients encompasses a spectrum of clinical presentations, including acne, hirsutism, oligomenorrhea, amenorrhea, virilism, and ovarian cysts. Androgen excess is a clinical and chemical feature of idiopathic hirsutism, late-onset forms of congenital adrenal hyperplasia, and polycystic ovarian disease; in some cases, functional hyperandrogenism is discussed. We recommend screening for hyperandrogenism by measuring blood levels of testosterone, dehydroepiandrosterone sulfate, and Δ4-androstenedione, while others propose a first dexamethasone suppression test for evaluation of free testosterone, dehydroepiandrosterone sulfate, and cortisol. Treatment will be chosen according to particular symptoms such as acne, hirsutism, obesity, or oligomenorrhea.