Background. Hepatic ischemia-reperfusion (HIR) is a severe condition that is seen after hepatic arterial injury and in hepatic grafts in living donor transplantation. HIR not only causes liver injury by lipid peroxidation, but also stimulates systemic and portal endotoxemia. Also, lipopolysaccharide (LPS) induces hepatic injury mediated by inducible nitric oxide synthase (iNOS). There is little knowledge on the role of specific iNOS inhibitors in prevention of HIR injury followed by LPS administration. The aim of this study on a LPS induced HIR model was to investigate the effect of aminoguanidine (AG) administration on hepatic tissue iNOS expression and lipid peroxidation when given before or after LPS.