The lack of biologic markers for Alzheimer's disease and vascular dementia, the controversy regarding the definition of vascular dementia, and the new evidence of vascular risk factors for Alzheimer's disease suggest that the traditional differentiation between Alzheimer's disease and vascular dementia is no longer very clear. We believe that both vascular and degenerative mechanisms contribute to the development of dementia, especially in very old age. The question of whether they are two independent parallel processes or interacting pathologies needs to be clarified.