IN 1945 the use of amorphous penicillin was being suggested as a mode of treatment for syphilis of the central nervous system. A few articles had appeared indicating that the treatment had increased efficacy over the modes of therapy then in vogue, and it seemed desirable to check these impressions. Therefore, in September, 1945, an investigative project was set in motion at the Ypsilanti State Hospital. The patients with dementia paralytica committed to the hospital were suffering from the usual severe type. Criteria for the selection of patients in the groups to be studied were considered important. It was decided to divide the patients entering the hospital with dementia paralytica into five groups, taking them as nearly as possible in rotation. The criteria necessary for the patients to be considered were (1) that they not have had penicillin therapy prior to their admission to the hospital, and (2) that their