1. Previous history of rasburicase exposure and history of administration of a repeat (2nd) series of rasburicase injections (in the context of supportive care for relapsing leukemia/lymphoma) and subsequent development of either a hypersensitivity reaction (HSR) or loss of uricolytic activity (defined as failure to achieve uric acid level of < or = 7.5 mg/dl measured 48 hours after the first rasburicase injection).