Abstract 1. 1. It is felt that quantitative protein determinations on cerebrospinal fluids should be carried out routinely as an aid to diagnosis. 2. 2. A rapid, simple, volumetric method for the quantitative determination of the total protein content of cerebrospinal fluid is described. 3. 3. The principle is the precipitation of protein by Tsuchiya's reagent, centrifugalization in a finely calibrated centrifuge tube and comparison with a similarly treated standard protein solution. 4. 4. The total protein in 23 normal lumbar fluids varied from 17 to 40 mg. per cent with an average of 29. 5. 5. A table containing the total protein determinations of 359 selected cases is presented. 6. 6. Total protein values of different observers in various pathologic conditions are tabulated.