BACKGROUND: Postmortem studies have documented abnormalities in the medial orbital frontal cortex in depressed patients. In this study we evaluated whether atrophy of this region can be identified in older depressed patients using magnetic resonance imaging. METHODS: Twenty elderly patients meeting DSM-IV criteria for major depression and 20 matched control subjects were studied. The orbital frontal cortex was measured in both hemispheres using magnetic resonance imaging. RESULTS: Depressive patients had reduced volume in the total orbital frontal cortex, right orbital frontal cortex, and left orbital frontal cortex. CONCLUSIONS: Our finding of a reduction in orbital frontal cortex volume in both sides of the brain suggests that this region of the brain may have a critical role in the development of depression and raises questions about the etiology of the changes.