Two-dimensional electrophoresis isolates the various proteins in the CSF in peaks ; this a method which gives very reliable results ; the height of the peaks has a certain quantitative value, similar to that obtained with electro-immunodiffusion. The peaks visible in the CSF can be increased separately -- mainly the "alpha 2", "alpha 2 beta", the IgA and IgG peaks -- in another type of recording, the height and number of the peaks may be increased, indicating the presence in the CSF of normally absent protein originating in the serum. An increase in the "alpha 2" or "alpha 2 beta" peaks is not specific, but it is always indicative that the development of a neurological process is under way ; the increase of IgG and IgA retains its character of great specificity in evolutive inflammatory conditions. Multiple peaks indicate the passage of serum proteins into the CSF in oedematous and destructive processes, in expansive or compressive processes and in polyradiculoneuritis. This method with its well-codified technique, which may be carried out on an unconcentrated CSF without risk of denaturing the proteins, may be carried out routinely in clinical practice with human anti-serum immune serum or with more specific serum, anti CSF for example, which seems to give quite reliable results.