We estimated survival of patients with early onset Alzheimer's disease (AD) or vascular dementia (VaD) presenting to psychiatric hospitals in Scotland (1974-1988) and related this to age, gender and socio-economic variables. Hospital records of 1794 early onset dementia patients were reviewed. We identified 451 patients with early onset AD and 384 with VaD. Survival to death was calculated from symptom onset and presentation. Small geographical areas (postcode sectors) were classified by urban/rural category and deprivation score. Five-year survival from presentation of early onset AD was 32% for men and 43% for women compared to 22% for men and 36% for women with VaD. We conclude that increased age at presentation was associated with shorter survival in early onset AD and VaD. Socio-economic deprivation was associated with longer survival in VaD. The effects of urban/rural score were accounted for by the major effects of socio-economic deprivation.