295 newly diagnosed Multiple Sclerosis (MS) patients were investigated for interdependence of CSF abnormalities: leukocyte count, CSF/serum albumin ratio, CSF IgG index and intrathecal synthesis of oligoclonal IgG. Only 7% of patients had no CSF abnormality. The most frequent abnormal finding was the presence of intrathecal synthesis of oligoclonal IgG. Polyacrylamide isoelectric focusing appeared more sensitive than agarose electrophoresis for the detection of abnormal CSF fractions. CSF IgG index had low negative and high positive predictive value when compared with electrophoretic methods. Suspected MS had the lowest frequency of abnormal CSF parameters. Patients with oligoclonal CSF bands (OB+) did not differ in age, sex, disease duration or annual bout rate from patients without oligoclonal bands (OB-). CSF leukocyte count was higher in OB+ than in OB- patients. Low CSF cell count was a hallmark of progressive disease. In OB+ patients CSF cell count correlated with CSF IgG index during the first five years of disease and declined with increasing disease duration. In later disease phases CSF IgG index correlated negatively with CSF/serum albumin ratio. 5 years follow-up of this series of patients is in progress to assess the diagnostic and prognostic values of CSF abnormalities in Multiple Sclerosis.