Veno-occlusive disease of the liver (VOD) is an important complication in hematological transplantation. The aim of this study is to analyze the risk factors for VOD and other forms of liver toxicity in a cohort of 180 peripheral stem cell transplants performed in our Center. We find that elevated pretransplant levels of serum ferritin are the most important risk marker for VOD. We believe that ferritin reflects damage induced by oxygen radicals resulting from iron-mediated catalysis. We also discuss different risk factors for VOD and other forms of liver toxicity, suggesting diferent pathogenic mechanisms.