The content of Cl, Na, K and inorganic P was studied in the CSF of 25 patients. The CSF samples were normal in respect to pressure, aspect, color, cytology and protein content. The results of reactions for globulins and of the complement fixation tests for syphilis and cysticercosis were negative in all of them. CSF samples were obtained from patients with chronic neurologic conditions. They had no evidences of metabolic disturbances and were not accompanied by acute episodes such as convulsions. The concentrations of the inorganic components studied are reported in table two and their estimatives in table three. No influences of the sex, the age and the color of the patients upon the concentration were found. It was verified a positive correlation between Cl concentration and the concentration of Na and K. A negative correlation was found between the concentration of Cl and inorganic P. The values of such correlations are significant.