THE PROPER evaluation of success in treatment of neurosyphilis has always been a problem. When Wagner-Jauregg reported the beneficial effect of malaria in treatment of dementia paralytica twenty-seven years ago, there were no objective criteria to prove his point other than clinical improvement. Since spontaneous remissions are common in dementia paralytica, most authorities insisted on an extended period of observation before accepting malaria as a therapeutic agent. A few years later it became obvious that fever therapy, unlike any previous form of treatment, at least prolonged the life span of the patient with dementia paralytica. However, it still remained uncertain whether the therapeutic success would be permanently maintained, i. e., whether the disease process had been definitely arrested. To this the clinical follow-up of the patient failed to give an adequate clue. As time went on, it was found that reversible and irreversible signs and symptoms could exist side by