The current hypothesis for the pathogenesis of childhood idiopathic nephrotic syndrome (INS) favors the involvement of a T cell-mediated immune response. Various cytokines derived from T cells may play a critical role in INS. Previous studies have measured serum or urine cytokine levels and suggest an imbalance of the T cell-mediated immune response. To elucidate the true profile of T cell-derived cytokines, we determined interleukin (IL)-2, interferon (IFN)-gamma, IL-4, IL-10, and tumor necrosis factor (TNF)-alpha mRNA expression in children with INS. We collected mRNA from peripheral blood mononuclear cells together with plasma and urine from nine children in the acute and remission phases of INS. Expression of IL-2, IFN-gamma, IL-4, IL-10, and TNF-alpha mRNA was determined by a quantitative real-time PCR assay. Plasma and urine cytokine concentrations were measured using a specific enzyme-linked immunosorbent assay. These data were compared between the acute and remission phase in the same patients. The IL-2 mRNA levels were significantly higher in the acute phase than in the remission phase, whilst no significant difference was found in the other cytokines investigated. There was no significant difference in the plasma and urine cytokine concentrations between the acute and remission phase. Our results indicate increased expression of IL-2 mRNA in the acute phase of INS, suggesting that IL-2, at least in part, might be involved in the pathophysiology of childhood INS.