[Abstract] Objective To investigate the effects of sevoflurane preconditioning on pulmonary matrix metalloproteinases(mmp-9) mRNA during partial hepatic ischemia-reperfusion lung injury in rats and mechanism involved. Methods fifty-four male Wister rats weighing 270-330g were randomly divided into 3 groups (n=18 each): sham operation group (group S): the hilum of liver was isolated but not clamped; partial hepatic ischemia-reperfusion (I/R): the left and median lobe of liver was occluded for 30min followed by reperfusion; sevoflurane preconditioning group (group Sev): 2．1％sevoflurane was inhaled for 30 min．and partial heptic I／R was induced after the end of inhalation in group Sev. Six rats in each group were chosen at 30，60 and 120 min of reperfusion and sacrificed, and lungs were removed for microscope examination of pathologic changes which were scored and for determination of wet／dry lung weight(W／D)ratio，MPO activity(by colorimetrie method)and the expression of MMP-9 mRNA(by RT-PCR).Results Compared with group S， the pathological score，the W／D ratio，MPO activity and expression of MMP-9 mRNA were significantly increased in groups I／R and Sev(P<0．05)．Compared with group I／R，the pathological score，the W／D ratio，MPO activity and expression of MMP-9 mRNA were significantly decreased in group Sev(P<0．05)．Conclusion Severe acute lung injury after partial hepatic I/R in rats is attenuated by sevoflurane．An inhibition of MMP-9 mRNA expression in lung tissues may be one of the mechanisms for that.