A group of 66 patients hospitalized for the treatment of closed head injury, were assessed for the presence of mood disorders during their hospital admission and at 3, 6 and 12 months follow-up. A total 28 patients met DSM-III-R diagnostic criteria for major depression at some time during the study (17 in the acute stage, 11 during follow-up). The mean duration of major depression was 4.7 months. However, there appeared to be a group of transiently depressed patients (41%) who where depressed inhospital but were no longer depressed at 3 months follow-up. Throughout the follow-up period, major depression showed a strong relationship with poor social functioning. There was not, however, a consistent relationship between depression and quantitative measures of either physical or cognitive impairment. Location of the brain lesion was associated with the development of major depression only in the acute stage. Transient depressive syndromes were associated with left dorsolateral frontal and/or left basal ganglia lesions.