The diagnostic criteria postulated by Poser necessitate clinical and laboratory CSF analysis for establishment of the diagnosis of definitive multiple sclerosis. The present paper reports methods for CSF examinations relating to multiple sclerosis with regard to the examinations suggested by the Charcot Foundation. In the course of CSF analysis, it is important to discriminate between the immunoglobulins present in normal amounts, those synthesized locally in pathological quantities and those penetrating across the damaged blood-CSF barrier. Normally, a parallel assay of CSF and serum specimens is carried out in the course of quantitative and qualitative protein analysis. In 37 patients with clinical multiple sclerosis, we determined the albumin and the immunoglobulin classes IgG, IgA and IgM, using laser nephelometry. An elevated IgG index was found in 76% of the cases, which points to local IgG snythesis and might be proof of the humoral immune response. The albumin quotient, which is suitable for examination of the integrity of the blood-CSF barrier, was within the reference range. Qualitative protein analysis was performed by means of electrophoresis on agarose-gel and isoelectric focusing. Agarose-gel electrophoresis revealed oligoclonal gammopathy in 68%, in contrast with the 91% demonstrated by isoelectric focusing. Comparison of the two kids of qualitative protein analyses indicated that isoelectric focusing was more sensitive for the detection of oligoclonal bands, in support of the literature finding.