The first decade of the 20th century saw a dramatic growth in knowledge of neurodegenerative disease, with new histological techniques leading to the identification for the first time of distinct clinicopathological conditions, including Alzheimer’s disease (AD). The last ten years of the century (‘the decade of the brain’) has seen similar breakthroughs in our understanding of the pathogenesis of neurodegeneration, largely due to the availability of the new techniques of molecular biology. Whilst much of the research has centred on the genetics of early-onset disease, the findings have direct relevance to the great majority of elderly patients with sporadic AD. There is now a realistic prospect, in the early part of the next century, of effective disease-slowing therapies for established disease and even preventive interventions for at-risk individuals.