【Abstract】Objectives To investigate the significance of kidney injury molecule-1 (KIM-1) changes in urine in patients with acute kidney injury (AKI). Methods Clinical presentations, and urine and serum samples were collected in patients admitted to Xiangya hospital in January to October 2008 with slight AKI (20 cases), medium-severe AKI (25 cases), wounded individuals by Wenchuan earthquake (25 cases), and end stage renal disease (ESRD, 20 cases) based on the RIFLE criteria. Urine and serum samples were also collected from 30 healthy controls. Urinary KIM-1 was assayed by ELISA, urinary N-acetyl-beta-D-glucosaminidase (NAG) by colorimetric method, serum superoxide dismutase (SOD) by xanthine oxidase method, and serum malonaldehyde (NDA) by thiobarbituric acid colorimetric method. The correlation between KIM-1 and NAG in urine was analyzed, and the sensitivity and specificity of urinary KIM-1 in the early diagnosis of AKI were evaluated using the receiver operator characteristic (ROC) curve. Results Urinary KIM-1 increased significantly in patients with slight and medium-severe AKI, as compared with that in ESRD patients and normal controls (P＜0.05). Urinary KIM-1 was higher in patients with medium-severe AKI than in slight AKI (P＜0.05). Urinary KIM-1 was positively correlated with urinary NAG, serum SOD and serum MDA, and it had the area under the ROC of 0.914 (P＜0.01). No statistically significant difference was found in urinary KIM-1 between ESRD patients and healthy controls (P＞0.05). Urinary KIM-1 was higher in wounded individuals by earthquake than in normal controls (P＜0.05). Conclusions Urinary KIM-1 is a useful marker for the early diagnosis of AKI. Higher urinary KIM-1 may relate to the AKI-induced oxidative stress.