Objective To explore whether the amount of lipocalin-2 in the biofluid could reflect the onset of sepsis-induced acute lung injury(ALI) in mice. Methods Lipopolysaccharide(LPS, 10 mg/kg) injection or cecal ligation and puncture(CLP) was performed to induce severe sepsis and ALI in C57 BL/6 male mice randomly divided into 5 groups(n=10 in each group): group A(intraperitoneal LPS injection), group B(intravenous LPS injection via tail vein), group C(CLP with 25% of the cecum ligated), group D(CLP with 75% of the cecum ligated), and the control group(6 sham-operation controls plus 4 saline controls). All the mice received volume resuscitation. Measurements of pulmonary morphological and functional alterations were used to identify the presence of experimental ALI. The expressions of lipocalin-2 and interleukin(IL)-6 in serum, bronchoalveolar lavage fluid(BALF), and lung tissue were quantified at both protein and mRNA levels. The overall abilities of lipocalin-2 and IL-6 tests to diagnose sepsis-induced ALI were evaluated by generating receiver operator characteristic curves(ROC) and computing area under curve(AUC). Results In both group B and group D, most of the “main features” of experimental ALI were reproduced in mice, while group A and group C showed septic syndrome without definite evidence for the presence of ALI. Compared with septic mice without ALI(group A+group C), lipocalin-2 protein expression in septic mice with ALI(group B+group D) was significantly up-regulated in BALF(P<0.01) and in serum(P<0.01), and mRNA expression boosted in lung tissues(all P<0.05). Lipocalin-2 tests performed better than IL-6 tests in recognizing sepsis-induced ALI cases, evidenced by the larger AUC of the former(BALF tests, 0.8800 versus 0.6625; serum tests, 0.8500 versus 0.7000). Using a dual cutoff system to diagnose sepsis-induced ALI, BALF lipocalin-2 test exhibited the highest positive likelihood ratio(13.000) and the lowest negative likelihood ratio(0.077) among the tests of lipocalin-2 and IL-6 in blood and BALF. A statistically significant correlation was found between lipocalin-2 concentration in BALF and that in serum(Spearman r=0.8803,P<0.0001). Conclusions Lipocalin-2 expression is significantly up-regulated in septic ALI mice compared with those without ALI. Lipocalin-2 tests with a dual cutoff system could be an effective tool in distinguishing experimental ALI cases. Objective To detect whether the amount of lipocalin-2 in the biofluid could reflect the onset of sepsis-induced acute lung injury (ALI) in mice. Methods Lipopolysaccharide (LPS, 10 mg / kg) injection or cecal ligation and puncture group A (intraperitoneal LPS injection), group B (intravenous LPS injection via tail vein), group C ( CLP with 25% of the cecum ligated), group D (CLP with 75% of the cecum ligated), and the control group (6 sham-operation controls plus 4 saline controls). All the mice received volume resuscitation. Measurements of pulmonary morphological and functional alterations were used to identify the presence of experimental ALI. The expressions of lipocalin-2 and interleukin (IL) -6 in serum, bronchoalveolar lavage fluid (BALF), and lung tissue were quantified at both protein and mRNA levels. abilities of lipocalin-2 and IL-6 tests to diagnose s epsilon-induced ALI were evaluated by generating receiver operator characteristic curves (ROCs) and computing area under curves (AUCs). In both group B and group D, most of the “main features ” of experimental ALI were reproduced in mice, while group A and group C showed septic syndrome for the presence of ALI. Compared with septic mice without ALI (group A + group C), lipocalin-2 protein expression in septic mice with ALI (group B + group D) was Significantly upregulated in BALF (P <0.01) and in serum (P <0.01), and mRNA expression was boosted in lung tissues (all P <0.05). Lipocalin-2 tests performed better than IL-6 tests in recognizing sepsis-induced ALI cases, evidenced by the larger AUC of the former (BALF tests, 0.8800 versus 0.6625; serum tests, 0.8500 versus 0.7000). Using a dual cutoff system to diagnose sepsis-induced ALI, BALF lipocalin- 2 test exhibited the highest positive likelihood ratio (13.000) and the lowest negative likelihood ratio (0.077) among the testsof the lipocalin-2 and IL-6 in blood and BALF. A statistically significant correlation found between lipocalin-2 concentration in BALF and that in serum (Spearman r = 0.8803, P <0.0001) regulated in septic ALI mice compared with those without ALI. Lipocalin-2 tests with a dual cutoff system could be an effective tool in distinguishing experimental ALI cases.