Background: Despite its negative consequences, little is known about the natural history of depression in the oldest old. Aims: To study the incidence, course and predictors of depression in the general population of the oldest old. Method: The Leiden 85-plus Study is a prospective population-based study of 500 people from their 85th to their 89th birthdays. Depressive symptoms were annually assessed with the 15-item Geriatric Depression Scale, using a cut-off of 4 points. Results: During a mean follow-up of 3.9 years, the annual risk for the emergence of depression was 6.8%. Poor daily functioning and institutionalisation predicted depression. Among the 77 participants with depression at baseline (prevalence 15%) the annual remission rate was ony 14%. In more than half of the participants with a remission of depression, we observed a relapse of depression during follow-up. No predictors of remission could be identified. Conclusions: Among the oldest old, depression is frequent and highly persistent. More active case-finding and treatment would be potentially rewarding.