Background/Purpose: Lupus nephritis (LN) is one of the most frequent manifestations of SLE and can be present in 60% of SLE patients. Kidney biopsy remains the basis of LN diagnosis. There is urgent need to identify biomarkers that alternative to renal pathology in lupus. Aim: To study urinary angiostatin in SLE and investigate their possible role as indicative of renal involvement to be used as alternative to biopsy. Methods: Angiostatin levels were measured in urine samples from 45 lupus patients and 14 healthy volunteers, renal biopsy was obtained from all patients Results: SLE patients had elevated urinary angiostatin as compared to controls (P < 0.001). Levels of urinary angiostatin were higher in patients with an active LN (lupus nephritis) than those with inactive LN (P < 0.001). In patients with LN urinary angiostatin correlated with the renal score of the Systemic Lupus Erythematosus Disease Activity Index. Urinary angiostatin levels varied significantly and there is significant positive correlation (P