Our experience with the clinical application of penicillin in the treatment of neurosyphilis is now in the early part of its third year. During this time certain impressions have been gathered which indicate the trend of the results of treatment. However, the period of observation is still too short to justify any attempt to make conclusive deductions as to the merit of penicillin in the treatment of neurosyphilitic patients. In fact it is well not to draw conclusions as to the success or failure of any method of treating neurosyphilis until a minimum of three years and preferably five years has elapsed since the treatment was started. Accordingly, this report is a brief summary of the observations on 100 patients who had neurosyphilis and who were treated by various systems in which penicillin was employed during the past two years. The reports in the literature are at variance as to