A follow-up study was made at the Boston Psychopathic Hospital of 165 non-luetic psychotic patients in whom the spinal fluid contained abnormalities. The patients were followed for an average period of three years. (1) In six, or 4 per cent, the abnormal findings were traced to errors in technique (laboratory error, or "bloody tap"). (2) In 70, or 42 per cent, confirmation was obtained for neurologic or metabolic conditions which were suspected at the time of the lumbar puncture as being responsible for the spinal fluid abnormalities. These conditions were: cerebral vascular disease, alcoholism, drug intoxication, encephalitis, brain trauma, brain tumor, multiple sclerosis, pellagra, and Huntington's chorea. (3) In 19, or 12 per cent, organic diseases were discovered in the follow-up study though at the time of the first spinal fluid examination, these diseases were not recognized. They were: cerebral vascular disease, brain tumor, alcoholism, myxedema, encephalitis, multiple sclerosis, intracranial tuberculoma, and Pott's disease of the spine. (4) In 70, or 42 per cent, the abnormal spinal fluid findings still remained unexplained. Thirty-five of these patients were schizophrenic, 17 manic-depressive.Abstract Teaser