OBJECTIVE: to provide information on epidemiology of dementia in Tuscany needed to plan for dedicated health and social services. DESIGN: analysis of pooled baseline data from 4 population-based longitudinal studies. SETTING: 4 municipalities in Tuscany. PARTICIPANTS: 4,056 elderly subjects enrolled in 4 longitudinal studies. MAIN OUTCOME MEASURES: age- and sex-specific dementia prevalence rates and estimated number of demented people, by degree of cognitive impairment and BADL disability in the elderly population of Tuscany. RESULTS: out of the evaluated subjects, 293 are demented. Prevalence of dementia increases from about 1 % in the 65-69 age group to about 28 % in the 90+ age group both among women and men. About 43% of the demented study subjects suffer from severe mental deterioration (MMSE < 14) and56% are disabled in at least one Basic Activity of Daily Living (BADL). We estimate that about 19 thousand demented elderly men and 40 thousand demented elderly women are currently living in Tuscany of whom 26 thousand severely mentally impaired and 34 thousand disabled in at least one BADL. The resulting overall dementia prevalence standardised on the Italian 65+ population is 5,3% for men and 7,7% for women. CONCLUSIONS: these estimates could be used as a basis for the evaluation and the planning of social and health care services dedicated to demented people