This work aimed to investigate the value of urinary tumor necrosis factor–like weak inducer of apoptosis (uTWEAK) as a biomarker for lupus nephritis (L.N.) activity.sixty patients with systemic lupus erythematosus (SLE) fulfilling the 1997 revised criteria for the classification of SLE as well as 20 age/ sex- matched healthy controls included in this study were subjected to full history taking, clinical examination, routine laboratory investigations, measurement of uTWEAK level as well as renal biopsy for patients with active L.N.uTWEAK levels were significantly higher in SLE patients with active LN compared to those without or with inactive renal disease and normal healthy subjects.