A graph for the evaluation of the CSF-protein profile is presented as a basic program for the clinical-neurochemical laboratory. The graph has the following advantages: Simultaneous information on the functional state of the blood-CSF barrier and the inflammatory response of the CNS; maximal sensitivity for the determination of a pathological local IgG production in CNS--with the possibility of calculating the IgG fraction in CSF originating from the CNS; minimal number of protein assays necessary (albumin and IgG in serum and CSF); suitable for the demonstration of the course of the disease in a single patient as well as for demonstration of a group of cases for statistical purposes. Complementary chemical investigations and the correspondence with the clinical diagnosis are discussed for a number of typical cases. Two different types of blood-CSF barrier dysfunctions are discriminated by a proportional and a dis-proportionate increase of the CSF/serum protein concentration gradients.