OBJECTIVES: To test the hypothesis that noninvasive urinary biomarkers may improve early identification, differentiate causes, and predict outcomes of acute kidney injury (AKI) in very low birth weight subjects. STUDY DESIGN: We performed 2 nested case-control studies to compare the ability of 6 urine biomarkers to predict AKI (rise in serum creatinine of at least 0.3 mg/dL) and mortality (death before 36 weeks postmenstrual age). RESULTS: Compared to subjects without AKI (n = 21), those with AKI (n = 9) had higher maximum neutrophil gelatinase-associated lipocalin (OR = 1.2 [1.0, 1.6]; P < .01; receiver operator characteristics [ROC] area under the curve [AUC] = .80) and higher maximum osteopontin (OR = 3.2 [1.5, 9.9]; P < .01; ROC AUC = 0.83). Compared with survivors (n = 100), nonsurvivors (n = 23) had higher maximum kidney injury molecule 1 (OR = 1.1 [1.0, 1.2]; P < .02; ROC AUC = 0.64) and higher maximum osteopontin (OR = 1.8 (1.2, 2.7); P < .001; AUC of ROC = 0.78). The combination of biomarkers improved predictability for both AKI and mortality. Controlling for gestational age and birth weight did not affect results considerably. CONCLUSIONS: Urinary biomarkers can predict AKI and mortality in very low birth weight infants independent of gestational age and birth weight.