Demographic, psychiatric, and electro-encephalographic (EEG) data were compared with brain autopsy findings for 73 elderly psychiatric patients. A late onset of depression (60+ years) was more likely than early onset to be accompanied by Alzheimer’s disease. There were strong associations between clinical and histopathological indicators of Alzheimer’s disease. This was particularly evident for diffuse EEG slowing. Clinical as well as histopathological indicators of Alzheimer’s disease were intensely related to EEG features, mainly EEG slowness (positive), reactivity to eye opening (negative) and dominant frequency (negative). Cerebrovascular pathology showed fewer EEG correlations. The results support the usefulness of the clinical electro-encephalogram in patients suspected to have Alzheimer’s