SUMMARYThirty-seven aspects related to the pathophysiology of serum and CSF immunoglobulins, including electrophoresis, immunoelectron-phoresis, CSF cytomorphology, and determination of the concentration of serum and CSF immunoglobulins, were studied in 64 patients with multiple sclerosis. The studies support the assumption that in addition to the immunopathological manifestations carried by immunocompetent cells in the CNS structures of patients with multiple sclerosis, the extraneural lymphoreticular system exhibits an abnormal activity, at least during certain phases of the disease. From our experiences in electrophoretic, immunochemical, and cytomorphological examinations of over 900 patients with different neurological diseases, no specific manifestations were observed which might allow, per se, the diagnosis of MS.