© 2001 by Taylor & Francis Group, LLC. I. INTRODUCTION The examination of cerebrospinal fluid (CSF) preceded neuroimaging and evoked potentials by decades as the first method to provide laboratory confirmation of a clinical diagnosis of multiple sclerosis (MS) (1). CSF continues to yield valuable clinical information for establishing the presence of MS and monitoring its activity (2,3). Because of its direct contact with the central nervous system (CNS), CSF has also been important for investigating the etiology and pathogenesis of MS.