BACKGROUND: Bolus steroids are usually administered prior to graft reperfusion in an attempt to provide protection against ischemia reperfusion injury (IRI). However, the anti-IRI properties of steroids have not been established. Living donor liver transplantation (LDLT) between identical twins provides a unique opportunity to study the natural production of cytokines during transplantation without the confounding influences of the alloimmune response or of immunosuppression in particular steroids. METHODS: A 38-year-old male with hepatitis C virus-related cirrhosis and multiple hepatocellular carcinomas received a hepatic right lobe graft from his identical twin. No immunosuppression was administered, not even intraoperative bolus steroids. IRI was assessed by serum transaminases as well as by proinflammatory interleukin (IL) IL-1beta, tumor necrosis factor (TNF)-alpha, IL-8 cytokines and for potent regenerative/anti-inflammatory (IL-6, IL-10) mediators. RESULTS: Despite no administration of steroids, low peak levels of serum transaminases were observed. Serum IL-6 and IL-10 dramatically and rapidly increased during liver transplantation, namely, 160 and 20 times higher than baseline, respectively. In contrast, IL-1beta and TNF-alpha remained low during and after transplantation and an increase in IL-8 was less obvious. CONCLUSION: Syngeneic LDLT without intraoperative bolus steroids is feasible, yielding no penalty in terms of IRI. A predominance of protective cytokines was observed in the absence of steroids. Thus, the concept that intraoperative administration of steroids is necessary to protect liver transplants from IRI must be revisited.