Prevalence studies on dementia generally show a higher risk in women than in men. American studies reported equal rates whereas European ones showed higher rates in women. Observational studies on hormone replacement therapy showed that treated women had a lower risk than untreated ones. Two large clinical trials in menopausal women did not find any protective effect of therapy with oestrogens or oestrogens plus progestinic hormones. However, as regards a potential protective role of female gonadal hormones on brain neurodegenerative diseases, this result cannot be considered conclusive since a large cohort study showed an increased risk of Alzheimer's disease (AD) in women who underwent early oophorectomy. A possible gender difference in the risk of AD is further supported by recent evidence suggesting that the brain's so-called cognitive reserve is reduced in women. The area of gender differences in AD and in neurodegenerative processes generally, although still largely unexplored, appears to offer great promise for the future development of better strategies of intervention for patients.