Intrathecal IgG synthesis has been studied in neurological patients by both quantitative and qualitative methods. An elevated correlation was found between IgG/Albumin quotient, IgG-Index and IgG SYN: moreover the appearance of oligoclonal IgG bands in CSF seems clearly related to high IgG Index values, as observed by statistical analysis. Nevertheless oligoclonal pattern in CSF is always present in diseases associated with immunological abnormalities, while quantitative parameters may be found elevated also in the diseases without a clear immunological disturbance. The authors stress the great importance of CSF examination by Isoelectric Focusing in the evaluation of intrathecal IgG synthesis in multiple sclerosis.