We reported a case of ALL complicated with acute pancreatitis caused by L-asparaginase (L-Asp). The patient was a 42-year-old man, who showed eosinophilia in peripheral blood and an increase of lymphoblast in bone marrow. He was diagnosed as ALL (L2) and treated by JALSG '87 protocol. Remission induction chemotherapy including L-Asp was administered by 5,000 IU i.v. for 10 days. The day after giving all dose of L-Asp, slight epigastralgia developed and then became severe. After two days, s-amylase was markedly elevated, and the patient was diagnosed as acute pancreatitis caused by L-Asp. He was treated conservatively, but hyperglycemia occurred. The epigastrial tumor was palpable and gradually grew in size. CT-scan and abdominal ultrasonography revealed pancreatic pseudocyst, so he was treated by percutaneous cyst drainage. The patient died of a relapse of ALL. The prophylaxis and early diagnosis of the pancreatitis and hyperglycemia caused by L-Asp are very difficult. We have to examine more cases and pay greater attention to the chemotherapy, including L-Asp.