The prognostic significance of cerebrospinal fluid electrophoresis and IgG-index has been investigated in 44 patients, of whom 10 had optic neuritis and 34 suspected, possible or probable multiple sclerosis. The predictive value of CSF oligoclonal banding for future disease dissemination is very high in the suspected multiple sclerosis subgroup, where after a follow-up of 4.4 years, 7 out of 7 band-positive patients displayed further disease activity. The absence of CSF oligoclonal bands seems to carry a relatively benign short-term (follow-up 3.4 years) prognosis in suspected MS cases.