We describe a patient with acute myelogenous leukemia (AML) who was complicated with severe tumor lysis syndrome (TLS) after a single day of chemotherapy; a previously unreported occurrence. A 48-year-old man was admitted because of fever and bleeding tendency, and was diagnosed as having AML: M1. His white blood cell count (WBC) was 66, 300/microliter with 96% myeloblasts. Chemotherapy with idarubicin and cytarabine was started. On the second day of the therapy, he developed acute renal failure (ARF) and deterioration of disseminated intravascular coagulation (DIC) with a marked reduction in his WBC (8500/microliter). Immediately after a diagnosis of tumor lysis syndrome (TLS), the following chemotherapy was discontinued. Hemodiafiltration and hemofiltration were initiated to treat the ARF, concomitant with anticoagulant and antifibrinolysis therapy for the DIC. Chemotherapy with daunorubicin and cytarabine was resumed on the 12th day, recognizing a regrowth of leukemic cells. Thereafter a complete remission was achieved without recurrence of the TLS.