The strategy against tumour lysis syndrome (TLS) had been hyperhydration, urine alkalinization, and allopurinol. Recently, rasburicase was added to the armament against this life-threatening condition. In Korea, rasburicase is used as a rescue therapy for cases with allopurinol-resistant hyperuricemia, because of the restriction by the National Health Insurance. We reviewed our experiences to re-assess the risk factors of TLS and the efficacy of rasburicase. Medical records were retrospectively reviewed for 396 children who were diagnosed as positive with acute leukemia and non-Hodgkin lymphoma between the years 2000 and 2009. The risk factors for TLS were analyzed statistically, and those before and after the availability of rasburicase were compared. Sixty eight patients (17.2%) had TLS. Multivariate analysis showed that pre-chemotherapy hypophosphatemia was a risk factor for TLS, in addition to the known risk factors of hyperuricemia and high lactate dehydrogenase concentration. The availability of rasburicase as a rescue therapy did not negate the importance of uric acid as a risk factor of TLS. Rasburicase as a second line treatment for intractable hyperuricemia was not effective in reducing the incidence of TLS. Pre-chemotherapy hypophosphatemia was a significant independent risk factor for TLS. Copyright © 2011 John Wiley & Sons, Ltd.