Hepatic veno-occlusive disease (HVOD) following bone marrow transplantation is potentially fatal. Criteria for diagnosis and starting treatment are mainly based on adult studies. Recombinant tissue plasminogen activator (rtPA) has been used with variable success. rtPA and heparin were given to 12 children (nine with immunodeficiency, two malignancy, one thalassaemia) with moderate to severe HVOD. Of the 12, 10 responded with a fall in bilirubin concentration; eight survived with complete resolution of HVOD. Four of the five patients with associated multiorgan failure (MOF) died despite rtPA treatment. One child suffered significant, and one minor, bleeding during rtPA treatment. A scoring system for quantifying the severity of HVOD in children is proposed, incorporating the criteria used to diagnose HVOD, risk factors for its development and also parameters reflective of the patient's general condition. This will facilitate early diagnosis and management of those cases which, if not treated promptly, are likely to deteriorate with an adverse outcome. Our experience suggests rtPA and heparin are an effective treatment for HVOD in children, with relatively little toxicity provided therapy is started before MOF develops.