The nephrotoxic potential of iphosphamide was evaluated in a retrospective analysis of all children receiving the drug at The Hospital for Sick Children in Toronto. The 25 children exhibiting nephrotoxicity did not receive more cycles or higher doses per square metre than the 78 with normal renal function. Similarly, the two groups received comparable doses and number of cycles of sodium 2-mercaptoethanesulphonate, and had similar rates of exposure to nephrotoxic drugs (except for cis-platinum). Children exhibiting nephrotoxicity were significantly younger (78.1 +/- 64.1 months) than those having normal kidney function (103.8 +/- 66.6 months) (P less than 0.05). Children exhibiting nephrotoxicity were more likely to have received cis-platinum prior to the iphosphamide (10/25, 40%) than those with normal renal function (14/73, 18%) (P less than 0.05). Nephrotoxicity was associated with a significant effect on growth. Careful follow-up of renal function should take place in children receiving iphosphamide, with special attention paid to children younger than 5 years of age and those who have received cis-platinum.