Cisternal cerebrospinal fluid (CSF) protein fractions were studied by paper electrophoresis. Through sub-occipital puncture samples were collected from 30 adults (age range from 15 to 45 years old) : 13 healthy people and 17 psychoneurotic patients, without past history of neurologic disease and/or evidence of organic affection. Syphilis serology was negative in all cases as well as CSF showed any abnormality in respect to pressure, aspect, color, cytology, total protein content, colloidal reactions, syphilis and cysti-cercosis complement fixation tests. Technical details were previously described; protein concentration was achieved by dyalisis against 30% poli-vinylpirrolidone at 4°C. Results are detailed in the table 1; mean values obtained for protein fractions were: pre-albumin 2.2%, albumin 51.6%, globulins: α1 5.0%, α2 8.7%, β 21.6% (including the τ fraction) and γ 10.9%. There was any significative difference between results found in normal people and in psychoneurotic patients. The values found are in agreement with those reported by Mumenthaler and Marki from data published until 1956. For comparison purposes the author's data are presented together with others obtained by several investigators (table 4). The results were compared to those found in sera from 30 adults selected in the same way and analysed by the same technique (table 2). Comparison showed similar results when the means found in respect to all sera and CSF samples were considered or when means found for seven cases in which it was possible to analyse CSF and serum proteins simultaneously were considered (table 3). Albumin (including pre-albumin) and α-globulins have similar relative patterns in both CSF and serum protein profiles, but those of β and y-globulins are disimilar. As far as to the sera, CSF proteins have relatively more jg-globulin (1.5 to twices) and less y-globulin (0.5 approximately).