Acute tumor lysis syndrome (TLS) has been reported in hematological malignancies, such as aggressive non-Hodgkin's lymphoma, acute lymphoblastic leukemia, and rarely, in other malignancies (solid tumors) in association with the administration of cytotoxic therapy. We report a case of a patient with chronic lymphatic leukemia (CLL) who developed autoimmune hemolytic anemia treated by high dose corticosteroids and, following this treatment, developed acute tumor lysis syndrome. Only one similar case has been reported recently. Clinicians should be aware that corticosteroids alone may produce this potentially life-threatening complication.