Six children (ages 2 to 14 years) with recurrent or poor risk primary brain tumors were treated with the '8 drugs in 1 day' chemotherapy regimen. As renal function deteriorated (median after five cycles), carboplatin was substituted in place of cisplatin at a median dose of 300 mg/m2 as a one hour infusion at hour three. Four patients also had their lomustine deleted and replaced by etoposide 100 mg/m2 at hour four. Compared to earlier cycles of chemotherapy, there was a moderate increase in transfusion requirement (especially platelets) but the incidences of fever and neutropenia were unchanged. Glomerular function as measured by nuclear glomerular filtration rate (GFR) remained unchanged or improved at the end of therapy. The severity of nausea and vomiting after substitution was markedly improved. Four of the six patients are still in complete remission 19 to 41 months after diagnosis or recurrence. It is feasible to substitute carboplatin and etoposide into the '8 drugs in 1 day' regimen when extramedullary toxicity is found.