41 patients with a depressive syndrome in middle age (mean age 55 years) were investigated. 19 of them had purely monopolar depressive syndromes without any organic features; 22 patients had a depressive syndrome associated with an organic brain disease (11 vascular, 11 primary degenerative disease). In all patients psychiatric and neurological investigations, a WAIS test, an EEG and a computer tomography were performed. The clinical findings were significantly different in both groups of depression but there was still a considerable overlap of symptoms. The EEG was inconclusive, the psychological test (WAIS) and the computer tomography showed the clearest separation between the organic and the nonorganic depressions leaving only 10% of inconclusive findings. Therefore, it may be concluded that the differential diagnosis of organic or nonorganic depressive syndrome in middle age cannot be made on the basis of one investigation on its own but on the combined results of clinical, functional, and morphological examinations.