ABSTRACTBackgroundDepression in old age is an important public health problem. The aims of this study were to report the prevalence of depression in the Medical Research Council Cognitive Function and Ageing Study (MRC CFAS), a community-based, cohort.MethodFollowing screening of 13 004 people aged 65 and over from a population base, a stratified random subsample of 2640 participants received the Geriatric Mental State (GMS) examination and were diagnosed using the Automated Geriatric Examination for Computer-Assisted Taxonomy (AGECAT) algorithm.ResultsThe prevalence of depression was 8·7% [95% confidence interval (CI) 7·3–10·2], increasing to 9·7% if subjects with concurrent dementia were included. Depression was more common in women (10·4%) than men (6·5%) and was associated with functional disability, co-morbid medical disorder, and social deprivation. Prevalence remained high into old age, but after adjustment for other associated factors, it was lower in the older age groups.ConclusionsThe prevalence of depression in the elderly is high and remains high into old age, perhaps due to increased functional disability.