The purpose of this paper is to report cerebrospinal fluid (CSF) findings in multiple sclerosis (MS) from our laboratory, to discuss the implications of CSF abnormalities in terms of diagnosis. Paired CSF-serum samples from of 1533 on 3893 patients with suspected neurological diseases over a 10 year period were analysed by routine laboratory microscopy and assays of immunoglobulin G by isoelectric focusing for the detection of intrathecal oligoclonal IgG. Patients were grouped further into four headings according to their disorders: MS (625 cases), definite (246 cases) probable (123 cases) and possible (256 cases) according to Poser, others inflammatory neurological diseases (91 cases), various non-inflammatory neurological disorders (732 cases) and uncertain neurological disorders (85 cases). Definite MS group (16%) was compared to non-inflammatory neurological disorders (48%). Important signs for activity of multiple sclerosis are observed. Cell counts were 10/microl in 71% (N < or =2/microl). Inflammatory cytology is observed after concentration and cytocentrifugation on slides with activated B-lymphocytes, lymphoplasmocytes and/or plasmocytes (76%), total protein concentration is increased in 37% (N < 0.40g/l), CSF/serum albumin quotient with age dependent references for the blood-CSF barrier dysfunction is increased in 26% (N < 0.65 x 10(-2)), IgG index for intrathecal synthesis of IgG is increased in 69% (N < 0.70), sensitive detection of oligoclonal IgG restricted to CSF by isoelectric focusing is positive in 91% (86-96%) with a specificity of 96% (93-99%).