Vascular dementia (VD) is the second most common cause of dementia in the elderly after Alzheimer's disease (AD). Prevalence estimates from community surveys indicate that, on average, 5% of persons over 65 and 15 to 20% of people over 80 suffer from "severe dementia". Clinico-pathological studies have shown that AD accounts for 50 to 60% of the cases and VD for about 10 to 20%; 20% of the patients have both disorders. The incidence rate of VD ranges from 7 per 1,000 person-years in normal volunteers to 16 per 1,000 person-years in subjects with risk factors for strokes, particularly high blood pressure. The only effective therapeutic approach to VD is the prevention of strokes, mainly through the treatment of hypertension; however, none of the therapeutic trials has included VD prevention as one of its treatment goals. Syst-Eur Study is a European placebo controlled trial which aims to determine whether morbidity and mortality are changed when elderly patients (60 years and over) with isolated systolic hypertension are treated. In this trial, the incidence of VD will be carefully recorded during the five year follow-up of the expected 3,000 patients. The present side project to the Syst-Eur trial will specifically address the following questions: does antihypertensive treatment reduce the incidence of VD?, and how do the cognitive functions of elderly patients change when treated with active or placebo treatment? The protocol is based on the administration of the MMS (Folstein) once a year to all patients. If the MMS score is 23 or less, a set of criteria will be used to establish the diagnosis of vascular dementia. A pilot study has demonstrated the feasibility of the trial. The main study is in progress.