Background: Acute lymphoblastic leukemia (ALL) has been the most common cancer reported in association with thrombosis in children. The incidence of symptomatic thromboembolism (TE) in children with ALL varies from 1 to 14% (Athale, 2003). We report a fatal case of multifocal small intestine and hepatic infarctions which abruptly developed during induction treatment for ALL. Case report: A 17-year-old boy was treated with 4 drug induction chemotherapy including L-asparaginase and prednisolone for ALL through a central venous catheter. Since the 9th day after initiating induction chemotherapy, hypofibrinogenemia (100 mg/dL), decreased antithrombin-III (80%) and aPTT prolongation were observed. He received repeated transfusions of fresh frozen plasma, platelet concentrate and AT-III supplementation. On the 14th day after injecting 5th dose of L-asparaginase, he developed abdominal discomfort and vomiting. Pancreatic enzymes were normal and abdominal ultrasonogram showed normal findings. However, in 12 hours, hematochezia and hypotension developed. Abdominal computed tomogram revealed small bowel infarctions involving ileal loop with pneumatosis intestinalis, intrahepatic portal vein gas, and multifocal infractions in the liver. He was diagnosed as acute panperitonitis with TE of mesenteric vessels, and underwent an emergency small bowel resection and ileostomy. Unfortunately, he died on the next day. Tests of inherited prothrombotic state were not performed. Conclusion: A serious TE in this case, although rare, may occur at any time during chemotherapy in cancer patients. The high suspicion of TE is needed in cancer patients with potential risk factors such as the use of central venous catheter, chemotherapy including L-asparaginase, or corticosteroid.