The effects of hypothermia depend of the cooling technique, level of hypothermia and tissue status (1). A new alternative approach to preserving isolated organs is hypothermia preconditioning, in which hypothermia perfusion is applied before ischaemia/reperfusion, improving tissue metabolic status and decreasing oxidative stress damage in isolated heart (2). Here, we determined the effects of a model of hypothermic preconditioning in liver when applied before ischemic/reperfusion by means of tissue damage indicators and oxidative stress parameters released in perfusate. Rats (male, 200-250g) were anesthetized with sodium pentobarbital (60 mg.g-1 i.p) and they underwent laparatomy. Liver were perfused with Krebs Henseleit buffer equilibrated with 95% O2/5% CO2 and placed in an IPRL system. Livers were randomly divided in two experimental groups: preconditioning + ischemia/reperfusion (PC+IR), and ischemia/reperfusion alone (IR), both n=5. The temperature of the medium varied according to group: 10 min of hypothermic perfusion (22 °C) + 10 min of rewarming (37 °C) in PC+ IR and, 20 min of normothermic perfusion (37 °C) in IR. All livers then underwent 40 min of ischemia and 20 min of reperfusion. The levels of oxidants (TBARS, NOx), antioxidants (thiol groups) and tissue-damage indicators (ALT, proteins) were measured at baseline (Basal), just before ischaemia induction (Pre-I), after ischaemia and 10 minutes of reperfusion, (Post-I 10) and after ischaemia and 20 minutes of reperfusion (post-I 20). The parameters evaluated were mostly similar in the pre-ischemic samples with the exception of thiol groups. At the end of reperfusion tissue damage indicators (ALT and proteins) were significantly higher in IR than in PC+IR livers.TBARS and NOx ialso increased while antioxidants fell in perfusate (Table 1). Hypothermic preconditioning improved antioxidant content and attenuated the hepatic oxidant damage induced by ischemia/reperfusion.