Abstract: To evaluate the value of ~(99)Tc~m labeled human serum albumin(~(99)Tc~m-HSA) in monitoring acute lung injury(ALI) induced by lipopolysaccharide(LPS) in rats,twenty adult Wistar rats are given ~(99)Tc~m-HSA intravenously,and are randomly divided into four groups 30 min later.The control and LPS group are given intravenous injection of 0.9% saline and LPS 8 mg/kg respectively.The ketamine and aminoguanidine group are given intraperitoneal injection of ketamine 4 mg/kg and aminoguanidine 20 mg/kg respectively just 30 min after administration of LPS 8 mg/kg.All of the four group rats are killed by blood letting at 3 h post-injection of ~(99)Tc~m-HSA.Pulmonary permeability index(PPI) and the ratio of lung wet weight and dry weight(W/D) is calculated.The results of PPI and W/D in control and LPS group are 95.58±11.32 and 5.38±0.24,6.61±0.18 and 4.19±0.11,respectively.The PPI and W/D in LPS group are much higher than that in the control group(P<0.01).The results of PPI in ketamine and aminoguanidine group are 36.80±7.22 and 33.54±(6.22),respectively.The PPI in ketamine and aminoguanidine group are lower than that in the LPS group(P<0.01),but still higher than that in control group(P<0.01).There is no difference in PPI between the ketamine and aminoguanidine group(P>0.05).So ~(99)Tc~m-HSA is an effective tracer in monitoring ALI induced by LPS in rats.