Both cell-mediated immunity and humoral factors are involved in the pathogenesis of Guillain-Barré syndrome (GBS). Intravenous immunoglobulin (IVIG) has been reported to be a practical, effective and safe treatment in childhood GBS, although the mode of action of IVIG remains uncertain. We studied pro-inflammatory cytokines (interleukin-2, interleukin-1 alpha and tumor necrosis factor-alpha) in plasma and cerebrospinal fluid (CSF) and lymphocyte subsets in peripheral blood both in the acute phase and in the recovery period in six children with GBS treated with IVIG. Flow cytometry was used to determine the subsets of lymphocytes in peripheral blood, and cytokines analyses were performed by using ELISA technique. Results were compared with a control group of 20 healthy children. A standard protocol of IVIG (400 mg/kg/day for 5 days) was administered to all the patients. Plasma interleukin-2 concentrations and the number of HLA DR+ active T cells in peripheral blood were significantly higher in the acute phase of the disease than in the recovery period and in healthy controls. There was no significant difference in the other cytokine concentrations in plasma and CSF or in the other lymphocyte subsets in peripheral blood. Our data indicate that IVIG may provide its possible therapeutic effect by acting in the cell-mediated immunity in GBS patients.