Chronic inflammatory demyelinating polyneuropathy (CIDP) is thought to be an inflammatory autoimmune disease against peripheral myelin. Recently several animal models have suggested that preferential activation of Th1 cell response is central to the pathogenesis of this disease. We studied the function of CD4 positive T cell subsets, Th1 cells and Th2 cells by analyzing their representative secreting cytokines. Th1 cells secrete Interferon gamma (IFH gamma) and Th2 cells secrete Interleukin 4 (IL4). Using enzyme linked immunospot (ELISPOT) assay, a very sensitive single cell analysis system, we enumerated IFN gamma and IL4 secreting peripheral blood lymphocytes in patients with CIDP. Also we examined these cytokines in supernatants of cultured peripheral blood lymphocytes by a very sensitive enzyme linked immunosorbent assay (ELISA), Immunodot assay and westernblot assay. In culture supernatants of CIDP patients' peripheral blood lymphocytes, the levels of both IFN gamma and IL4 were higher during the exacerbation stage than the remission stage. In the remission period, though the levels of IFN gamma and IL4 were low in the supernatants, the ELISPOT assay revealed that the number of IL4 secreting cells was elevated compared with that of IFN gamma secreting cells. Our results suggest that the switch from Th1 to Th2 might play an important role in inducing the remission stage in patients with CIDP.