The prevalence of dementia in elderly people living in the community was compared using data from Zaragoza (Spain) and Liverpool (UK). A standardized interview, the Geriatric Mental State (GMS), was administered to a random sample of 1070 persons in Liverpool and 1080 in Zaragoza. Using diagnoses derived from the GMS-AGECAT package we found no significant difference between the prevalence of dementia in Zaragoza (7.4%) and Liverpool (5.0%). The expected increase in prevalence with age was found, but the two cities did not appear to differ in the relationship between age and prevalence. No sex difference was apparent, and the two cities do not differ in the relationship between sex and prevalence.