The central nervous system is an important target for sex steroid hormones. During the climateric period the rapid decline of gonadal steroids causes neuroendocrine changes in different areas of the brain. The failure of gonadal hormone production brings specific symptoms due to the central nervous system derangement. At the hypotalamic level estrogen withdrawal gives rise to vasomotor symptoms, eating behavior disorders and altered blood pressure control. Psychological disturbances such as depression, anxiety, irritability and mood fluctuation are related to estrogen-induced changes in the lymbic system. The hypothesis of specific neuroanatomical and neurophysiological effects of estrogen on the brain may also explain the correlation between estrogen deficiency and cognitive disturbances such as Alzheimer's type dementia (AD). The increasing interest in the influence of sex steroids on brain function has focused attention on hormonal replacement therapy. Clinical and epidemiological studies have demonstrated that estrogen therapy exerts a positive effect on vasomotor instability and improves psychological disturbances. The positive effects of estrogen on mood are probably related to its stimulatory action on adrenergic and serotoninergic tone. Estrogen may influence the cognitive function through different biological actions. Estrogen administration increases total cerebral and cerebellar blood flow, cerebral glucose administration and improves cholinergic tone, a key neurotransmitter in learning and memory. The evidence suggests that hormone replacement therapy may reduce the relative risk of developing AD. Progestagens and androgen may also have a role in the control of mood disorders. At present, few data are available regarding the influence that selective estrogen receptor modulators, a new class of compounds, can exert on the brain.