Binding of monoclonal IgM antibodies in serum to antigens of the peripheral nervous system such as MAG and SG(L)PG was measured by various non standardised methods. In this study we evaluated a new commercially available IgM anti-SGPG ELISA (Bühlmann Laboratories AG, Switzerland). The results were compared with three different markers and methods: (1) an in-house thin-layer overlay chromatography for IgM reactivity against sulfated glucuronosyl paragloboside (SGPG) antibodies (gold standard), (2) an indirect immunofluorescent assay for detecting IgM antibodies against myelin, and (3) IgM anti-MAG antibodies, a commercially available Kit based on ELISA technology, manufactured by Bühlmann Laboratories AG. 147 patient sera with anti-MAG/SGPG neuropathy and 121 control sera from patients with peripheral neuropathy were analysed. The anti-SGPG autoantibody ELISA turned out to be a very reliable commercially available test with no technical difficulties and both, excellent sensitivity (0.98), and specificity (0.98) for detecting MAG/SGPG antibody-mediated demyelinating neuropathies. Anti-SGPG antibody titers have pratical implications for both, management and follow-up of neuropathies treated with rituximab.