Intravesical alum irrigation is the safest and most effective method of treatment for intractable hematuria. Systemic absorption is reported to be minimal and there have been no reported deaths following its use. We describe an elderly man with compromised renal function (serum creatinine 420 mumol./l.) who was treated with 1% alum irrigation for 48 hours for hematuria due to inoperable bladder cancer. He received a total of 9.6 l. during 48 hours, which controlled the bleeding. After cessation of the alum he became lethargic, suffered respiratory depression and died the next day. Laboratory data showed mild metabolic acidosis and increasing daily aluminum levels that peaked at 7,014 nmol./l. (toxic greater than 2,000) beginning on the day after treatment was commenced. The efficacy and safety profile of alum irrigation is discussed.