The authors describe four elderly patients with Binswanger's disease in whom depression was prominent. Therapy with antidepressant drugs in three patients produced major improvement in psychological and physical functions. The one patient who could not be given an adequate course of antidepressant therapy because of intercurrent illness improved spontaneously after many months. The authors conclude that depression associated with Binswanger's disease is reversible despite persistence of neurological abnormalities. They speculate that this depressive syndrome is an example of organic affective disorder due to diffuse subcortical white matter ischemic lesions of the cerebral hemispheres and discuss the possible neuroanatomical basis of the depression.