Hirsutism is the presence of terminal (coarse) hairs in females in a male-like pattern, affecting between 5% and 15% of women, depending on definition. Hirsutism has a significant negative impact on psychosocial development and is usually a sign of an underlying endocrine abnormality-namely, androgen excess. The most common cause of androgen excess is the polycystic ovary syndrome (PCOS), with 21-hydroxylase-deficient nonclassic adrenal hyperplasia, the hyperandrogenic insulin-resistant acanthosis nigricans syndrome, androgen-secreting tumors, and androgenic drug intake occurring less frequently. However, although 70-80% of patients with androgen excess demonstrate hirsutism, this sign may be less prevalent among women of Asian extraction. Conversely, not all hirsute patients have evidence of detectable androgen excess, as 5-15% of these women have "idiopathic hirsutism," with normal ovulatory function and androgen levels. There is a strong familial predilection for hirsutism, primarily because the underlying endocrine disorders (eg, PCOS) and the factors regulating the development of hair growth (eg, androgen receptor activity, 5alpha-reductase activity) have a strong genetic component. The diagnostic evaluation of the potentially hirsute patient first involves confirming the presence of hirsutism and then excluding associated or etiological abnormalities and disorders (eg, ovulatory dysfunction, adrenal hyperplasia, diabetes, thyroid hormone abnormalities). Treatment should be undertaken using combination therapy, to possibly include 1) hormonal suppression (oral contraceptives, long-acting gonadotropin-releasing hormone analogues, and insulin sensitizers), 2) peripheral androgen blockade (spironolactone, flutamide, cyproterone acetate, or finasteride), and 3) mechanical/cosmetic amelioration and destruction of the unwanted hairs (electrology and, potentially, laser hair removal). The application of eflornithine hydrochloride 13.9% topical cream may also be useful to ameliorate unwanted facial hair growth. Overall, although hirsutism is a frequent and distressing abnormality often signaling an underlying endocrine disorder, a systematic approach to evaluation will uncover the etiology, and combination therapy will provide satisfactory treatment for most patients.