The authors found that all but 3 of 80 randomly chosen patients in a Veterans Administration hospital who had been given a primary nonspecific neuropsychiatric diagnosis (organic brain syndrome, organic psychosis, chronic brain syndrome, etc.) could be assigned to specific diagnostic categories. Diagnosis was based on chart review and thorough neurological and clinical evaluation. Senile and alcoholic dementia and Korsakoff's syndrome were seen most often, and 15% of the patients were diagnosed as having functional disorders of the mental state. The authors review the organic brain syndrome diagnosis in light of this and other evidence. They believe that fractionation into more specific diagnoses is essential to further understanding of this group of diseases. Use of the general term can result in inappropriate or no treatment; further, it hampers essential psychological, pharmacological, and biomedical research on these disorders.