The Hisayama Study, which is a population-based prospective cohort study, has been investigating incidence and risk factors for dementia since 1985. In the present analysis, 828 dementia-free subjects, aged 65 years or older, were followed for 17 years. During the follow-up period, 275 subjects were newly diagnosed to be dementia. They were divided into 124 cases of pure Alzheimer’s disease (AD), 81 of pure vascular dementia (VD), and 31 of mixed type of dementia (AD+VD). Hypertension was a risk factor for VD but not for AD. On the other hand, glucose intolerance was a strong risk factor for both AD and VD.