bout 40–50% of all patients with systemic lupus erythematosus (SLE) patients are associated with significant morbidity and a poor prognosis. The transforming growth factor β-1(TGF-β1) is a member of cytokines families which has emerged as an important player in the pathogenesis of autoimmune diseases, including SLE. In this study we aimed to evaluate TGF-β1 as a noninvasive diagnostic test for early diagnosis of LN and to assess the correlations between TGFβ-1 and clinic-pathologic characteristics as well as disease activity of SLE. This case-control study included 188 patients with SLE, stratified into two subgroups LN group and Non-LN group. We assessed diseases activity by SLE disease activity index and measured TGEβ-1 by using ELISA. Our results showed that LN patients had significant lower values of serum TGF-β1 compared with non-LN patients (P<0.001). Moreover, there were significant differences between LN histopathological classes. The lowest levels values of serum TGFβ1 was in Class V. There were significant negative correlations between levels of TGF-β1 and SLEDAI, fever, arthritis, proteinuria, hematuria, serum creatinine, thrombocytopenia, lymphopenia, ESR, ANA, pus cell and cellular cast's, all (P<0.01). In lupus nephritis patients, TGF-β1 levels were positively correlated with eGFR, C3 and C4 (P<0.001). Linear regression analysis revealed that, eGFR, CRP, thrombocytopenia, and serum creatinine were independently correlated with TGF-β1 among lupus nephritis patients (P<0.001). According to Receiver Operating Characteristic analysis, the sensitivity and specificity of TGF-β1 were 91% and 65.5%, respectively in the diagnosis of LN among SLE patients. As LN group had significantly lower values of serum TGFβ1 and the values further decreased with more damage of kidney tissues and progression of SLE activity. We conclude that serum