Focusing on CD4(+)CD25(+) regulatory T lymphocytes (T(reg)), we studied the gene expression of T(reg) functional molecules in peripheral blood lymphocytes of patients with paraneoplastic neurological syndrome (PNS), including Lambert-Eaton myasthenic syndrome (LEMS) with small cell lung carcinoma (SCLC) and anti-Hu- or anti-Yo-antibody-positive PNS.