We have reported previously that poorly educated elderly people and those of low social class were at much increased risk of scoring below the customary cut-point on the Mini-Mental State Examination, a widely-used, brief cognitive screening test. As part of the same study, subjects who scored 23 or less on the MMSE out of a maximum of 30 points, and a sample of those who scored 24 or 25 points, were assessed by psychiatrists using a structured, diagnostic interview. Assuming that persons who scored 26 points or above were cognitively intact (our data suggest that 2% or less were not), neither educational attainment nor social class had any influence on the likelihood that subjects would be diagnosed as demented. Our data suggest that social and psychological factors contribute substantially to cognitive test scores and serve to emphasize the importance of detailed assessment procedures in epidemiological surveys of dementia.