This is a multi-center, 2 arm, open-label study;
* Arm A: Patients previously treated with a uricolytic agent;
* Arm B: Patients not previously treated with a uricolytic agent.
Patients receive rasburicase for 5 days and begin chemotherapy 4-24 hours after the first dose of rasburicase. Patients are followed at 14 and 35 days, at 3 and 6 months and every 6 months thereafter.