A case history is reported or renal failure during and after treatment with carboplatin for 3 days, total dose 750 mg/m2, in a conditioning regimen prior to autologous bone marrow transplantation. Pretreatment renal function was compromised after nephrectomy and chemotherapy with cisplatin. A decrease in glomerular filtration rate concurred with a decrease in excretion of platinum in the urine and an increase in urinary beta 2 microglobulin. Treatment with high-dose carboplatin in patients with impaired renal function and previous treatment with cisplatin may lead to further loss of renal function.