To elucidate the T helper 1 (Th1)/T helper 2 (Th2) balance in various inflammatory neuropathies, we measured the ratio of intracellular interferon-gamma (IFN-gamma)-positive to IL-4-positive cells (intracellular IFN-gamma/IL-4 ratio) by flow cytometry in peripheral blood CD4(+) T cells of 14 patients with mononeuritis multiplex (MNM), 12 patients with chronic inflammatory demyelinating polyneuropathy (CIDP), 10 patients with Guillain-Barré syndrome (GBS), 23 patients with neurodegenerative disorders and 36 healthy controls by intracellular labeling. The patients with MNM showed a significantly lower intracellular IFN-gamma/IL-4 ratio (P<0.05) and higher IL-4(+)/IFN-gamma(-) cell percentages (P<0.05) than the controls. The increase of IL-4(+)/IFN-gamma(-) cell percentages was especially prominent in MNM of unknown etiology (P<0.005). The patients with CIDP also showed significantly higher IL-4(+)/IFN-gamma(-) cell percentages (P<0.05) than the controls. The IL-4(+)/IFN-gamma(-) cell percentages were increased in some patients with GBS, but the difference was not significant compared with the controls. Thus, our results suggest that a Th2 shift is a characteristic of MNM and may play an important role in the development of the disease.