Oestrogens are formed in the ovary from androgen precursors which circulate at a higher concentration in the blood and have a greater production and secretion rate than oestrogens. Although the post menopausal ovary remains a source of testosterone (T) production there is a fall in total circulating androgens with age and this results from a combination of ovarian failure, decreasing adrenal secretion and peripheral conversion.This relative androgen deficiency is greater in women who have had bilateral oophorectomy, where T levels can fall by 50%, and is also present in premature ovarian insufficiency. It can also occur secondary to adrenal insufficiency or to medication such as the contraceptive pill, oestogen therapy and GnRH analogues. Sex hormone binding globulin (SHBG) binds T at such high affinity that only 12% of the hormone is free to act on the target cell. An increase in SHBG can result in decreased free T levels. Correlation between T levels and sexual function is unclear and measurement of free T is often not available.There is, however, evidence emerging demonstrating a role for T in normal sexual function, mood, cognitive function, well being, bone and muscle mass. The relationship between sexual desire and T is complex but reduced libido is a common symptom in menopausal women, particularly in surgically menopausal women and premature ovarian insufficiency. Testosterone replacement can improve sexual function and well being and androgenic side effects are uncommon. Unfortunately there are few licensed androgen preparations available for women.