Abstract： Objective To investigate the significance of interleukin-13 (IL-13) in patients with active lupus nephritis (LN).Methods Ten healthy volunteers and 16 patients with active LN were included in this study. The protein level of IL-13 in plasma was examined by enzyme linked immunosorbent assay (ELISA), and gene expression of IL-13 in peripheral blood mononuclear cells (PBMCs) by reverse transcription polymerase chain reaction (RT-PCR). Expression of IL-13 mRNA in renal tissue was studied by in situ hybridization (ISH) techniques.Results The level of IL-13 in plasma and the expression of IL-13 mRNA in PBMCs were significantly higher in LN patients than those in the controls ( P ＜ 0.001 ). Increased expression of IL-13 mRNA was detected in renal tissue of active LN patients compared to those in the controls ( P ＜ 0.001 ). Analysis of the linear correlation indicated that the level of IL-13 mRNA in the tubulointerstitial area in patients with active LN correlated with the concentration of serum creatinine (Scr), the glomerular activity index (GAl),the activity index of tubulointerstitium, and the level of serum C3 ( P ＜ 0.05 for each).Conclusion The elevation of IL-13 may play an important role inthe molecular pathogenesis of active LN.