To assess the prevalence of dementia and its subtypes in a population with a low level of education, and to determine whether there is any association between occupation, education and dementia. Cross-section study of the population, with a sample of 3,214 individuals representative of the population of Toledo, Spain, aged 65 years and older. The Mini-Mental State Examination (MMSE) was used in the first phase of the study to detect those individuals with cognitive deterioration. The second phase consisted of a semi-structured clinical interview and neuropsychological evaluation. Dementia and sub-types of dementia were determined using well-established diagnostic criteria. The process was applied using an algorithm to optimise diagnostic agreement. The overall prevalence of dementia, Alzheimer's disease and vascular dementia amounted to 7.6, 4.6 and 1.8%, respectively. A direct relationship was detected between these three entities and age. The prevalence of dementia was greater in women, illiterate persons and occupations which require less skill. Once adjustment had been made for other socio-demographic variables, only age was associated with the presence of dementia. The overall prevalence of dementia, Alzheimer's type dementia and vascular dementia increases with age. No clear association was found between education, occupation and dementia.