The three-stage East Baltimore Mental Health Survey, conducted in 1981 as part of the Epidemiological Catchment Area Program, provided an opportunity to assess the prevalence of dementia and specific dementing disorders in a community-based, cross-sectional sample of the population. From the 3,841 households originally sampled, 810 individuals were selected for clinical psychiatric evaluation. Forty-one individuals were given a provisional diagnosis and referred to Stage 3 for differential diagnosis, with 32 individuals completing this evaluation. Thorough clinical evaluation of these cases resulted in an overall prevalence of dementia of 4.5% in those 65 years of age and older. The prevalence of specific dementing disorders was Alzheimer's disease (AD) (2.0%), Multi-Infarct Dementia (MID) (2.0%) and Mixed Dementia (MD) (0.5%). Prevalence increased with age for all dementias: Non-Whites had higher rates of dementia than Whites; females had higher rates of AD while males had higher rates of MID; and the prevalence of AD increased with increasing education, whereas the prevalence of MID decreased with increased education. Although this study includes only a small number of cases, necessitating some caution in interpreting the results, these figures do represent an estimate of the prevalence of severe dementing disorders and provide a basis for further community study.