This paper is based on the study of the protein profile of the cerebrospinal fluid of 300 neurological patients. This material was analysed in the same way as that one performed by Matiar and Schmidt (1958) and it was found almost the same results. These findings suggested the great value of the cerebrospinal fluid gamma-globulin concentration in the neurological differential diagnosis. In order to enlarge these studies in our own material, it was tried to find some correlation between albumin and globulin fractions expressed in mg/100 ml. The logarithm of albumin concentration was plotted graphically against the logarithm of globulin concentration; each disease was noted down as different symbols. It was verified linear bilogarithmic correlation between albumin and each globulin fraction. Graphs with albumin/alpha-globulin or with albumin/beta-globulin showed absence of characteristic disease behaviour. On the contrary, the graph with albumin/gamma-globulin showed a typical behaviour for neurolues and brain cysticercosis data. Assuming that the cases of spinal block may very well indicate the condition where the changes of the spinal fluid proteins were due to a modification of permeability of the blood-brain barrier, it was calculated the regression equation for the various gamma-globulin concentrations of these cases. It was found that most of the cases of brain tumors, intracranial hemorrhages, meningitis and polyradiculoneuritis were in perfect agreement with the cases of spinal block, suggesting that in these cases the protein changes were due to a modification of permeability of the blood-brain barrier. On the contrary, the great majority of the cases of neurolues and brain cysticercosis did not follow this pattern, suggesting that there was an increase of the spinal fluid gamma-globulin which must be originated intrathecally. These findings point out to two different mechanisms in the changes of the protein profile of cerebrospinal fluid and, therefore, electrophoresis did not allow the diagnosis of a determined neurological disorder, but it shows the particular physiopathological mechanism involved.