Ventricular (n=27), cisternal (n=33) and lumbar (n=127) cerebrospinal fluid of "non-diseased" reference persons was investigated. The following measurements were taken: (1) Total protein, albumin, immunoglobulin A,G, M (IgA,G,M) in unconcentrated cerebrospinal fluid (CSF). (2) Protein fractions in the microzone electrophoresis of concentrated CSF. Albumin and IgG concentrations were highly correlated in all the samples, regardless of their origin. Therefore, bivariate areas of reference as well as interdependent regression coefficients were computed for the paired data. The regression lines of the 3 different areas of reference (ventricular, cisternal, lumbar) ran parallel to each other, displaced along the axis of the IgG concentration: approximately 10% of the lumbar IgG does not originate directly from serum. Although the albumin concentration increased 2.2 times, and the IgG 2.6 times, from ventricular to lumbar region, the concentration of pre-albumin decreased by a factor of 0.7. The concentration of IgA never surpassed the limits of detection set by this method (8 mg/I), in spite of its similarity to IgG regarding molecular weight and size. The observations strengthen the assumption that selective functions are present at the blood-CSF barrier. In 4 illustrative cases with a chronic inflammatory process, the discriminating power of the different reference areas was demonstrated. The findings should be evaluated in a multivariate manner, considering the location from which the sample was obtained.