Cerebrospinal fluid (CSF) samples from 10 patients with Multiple Sclerosis (MS) and 7 with other neurological diseases (OND) were studied in order to detect oligoclonal restriction of IgG subclasses 1,3 and 4. Agarose isoelectric focusing (AGA-IEF) followed by Western capillary blotting and immunoperoxidase staining with specific monoclonal antibodies were used. All MS samples showed oligoclonal IgG1 and 6 of them also had IgG3 or IgG4 bands. In the OND group only patients with subacute sclerosing panencephalitis (SSPE) and Guillain-Barré disease (GBD) showed CSF oligoclonal patterns for IgG subclasses. Our results demonstrate that in MS CSF other IgG subclasses beside IgG1 may display an oligoclonal pattern. The finding of more than one subclass in the same band indicates a microheterogeneous composition of these oligoclonal bands.