This study investigated the severity of dementia in relation to disease type and sociodemographic variables. The dementia cases were detected with a two-phase study design in a population aged over 74 years in Stockholm. The prevalence of questionable, mild, moderate, and severe dementia was 1.0, 3.1, 5.5, and 2.3 per 100, respectively. Women aged over 84 had the highest prevalence of severe dementia. More severe cases and a higher institutionalization rate were present for vascular dementia than for Alzheimer's disease. Fifty-five percent of the demented subjects but only 3% of the nondemented were institutionalized. The institutionalized demented subjects were affected mostly by moderate-severe dementia (88.6%), while the noninstitutionalized were affected more often by a questionable-mild form (68.3%).