OBJECTIVE To evaluate the role of urinary neutrophil gelatinase-associated lipocalin (uNGAL), or lipocalin-2, in systemic lupus erythematosus (SLE) patients as a biomarker of renal activity and flares. METHODS Fifty subjects were divided into three groups: the first group comprised 14 SLE patients with no renal disease, the second group 16 SLE patients with active renal disease, the third group 20 apparently normal volunteers. At the beginning of the study clinical and laboratory data including uNGAL were collected. All patients were followed up serially in visits. At each visit, urine samples were collected for measurement of uNGAL as well as for standard urinalysis and a urine protein/creatinine ratio. RESULTS A highly significant difference was seen in uNGAL in all studied groups. Correlation was noticed between uNGAL and laboratory parameters of renal disease activity. There was significant positive correlation between renal SLEDAI and uNGAL levels. uNGAL is a significant predictor for renal disease activity and renal flare. CONCLUSIONS The more active the renal disease, the higher the measured levels of uNGAL, suggesting that it is a potential biomarker of active renal disease. uNGAL can be a predictive biomarker that could be followed serially to forecast renal disease activity and lupus nephritis flare.