Neutrophil gelatinase-associated lipocalin (NGAL), is a small, robust protein expressed by neutrophils and various epithelia, including the renal proximal tubules. While initially proposed as a marker for infections and certain adenocarcinomas, it is now apparent that its early and dramatic rise in urine after renal injury may make it a useful marker of such injury. The current status of one of the most promising novel biomarkers, namely neutrophil gelatinase-associated lipocalin (NGAL), is presented in this review.