We studied the CSF and sera from 16 patients with MS to detect IgG antibody activity against normal CNS myelin and some of its proteic and lipidic components. IgG binding to a protein band of the same MW of myelin basic protein was detected by "immunoblot" in the sera and/or CSF of 25% of patients with MS and in none of the controls with OND. No IgG antibody reactivity against other components of CNS myelin was detectable in patients with MS, and immunoabsorption of the CSF of MS patients with CNS myelin did not modify the oligoclonal prophile of CSF IgG. Anti-myelin antibodies do not seem to represent the bulk of oligoclonal IgG in MS patients.