Abstract: Age-related brain disorders such as Alzheimer's disease (AD) are becoming increasingly prevalent. Estrogen replacement therapy (ERT) has shown potential both as a preventive measure and treatment for such disorders. Good evidence from basic science demonstrates that estrogen has multiple protective effects on neurons and neurotransmitter systems, and the effects of ERT can be demonstrated on the human brain using techniques such as functional neuroimaging. However, the evidence for estrogen's having a clinical role in the treatment and prevention of neuropsychiatric disorders is not well established. In this article we review research into the effects of estrogen on the human brain and we consider the role for ERT as a therapeutic tool.