Alzheimer's disease is the most frequent form of dementia and it is estimated that its prevalence will quadruple by the year 2050. In the past decade, a number of important new developments have provided insight in the pathogenesis, improved diagnosis and allowed therapy of dementia. Several new mutations in the amyloid protein precursor gene, presenilin-1 and -2 genes and the influence of the apolipoprotein E gene isotypes on the disease phenotype have been described. The role of secretases in the generation of amyloid in senile plaques has been determined and this may provide important new therapeutic approaches in the future. The role of vascular lesions in the development of dementia and relationship with the Lewy body variant of Alzheimer's disease have been refined. Acetylcholine is deficient in Alzheimer's disease and can be supplemented in part by treatment with acetylcholinesterase inhibitors. Recently, surprising results of vaccination with amyloid in a transgenic mouse model have opened a completely new perspective in the prevention and treatment of Alzheimer's disease.