Paraneoplastic neurological syndromes (PNS) are tumour-associated disorders, which are not caused by the tumour itself or its metastases. Since antineuronal autoantibodies can be detected in these patients, an autoimmune pathogenesis is suspected. Recently, autoantibodies against cerebellar Bergmann glia were found in patients with paraneoplastic Lambert-Eaton myasthenic syndrome and other paraneoplastic neurological syndromes associated with small cell lung cancer, and SOX1 has been identified as the corresponding antigen. SOX1-antibodies have been reported to be highly specific for paraneoplastic neurological disorders. However, increasing evidence exists that they may also be associated with other neuroimmunological disorders without an underlying tumour.