A combination of cisplatin and cytosine arabinoside was used to treat 21 patients with glioblastomas and 5 patients with recurrent grade II gliomas. Cisplatin 60-100 mg/m2 was given I.V. in 250 ml 0.45% saline and preceded by 500 ml dextrose 5% in 0.45% saline. Mannitol 50 g was given I.V. concurrently with the cisplatin. Cytosine arabinoside 500-1000 mg/m2 was given by rapid I.V. infusion immediately after the cisplatin. Of 25 evaluable patients, 10 (40%) experienced objective tumor shrinkage on CT scan, and 6 (24%) stabilized. There were 2 complete remissions. Patients who had had no prior treatment had a higher response rate (58%) than those previously treated (23%). Myelosuppression occurred in some patients 2-3 weeks after treatment. Gastrointestinal toxicity (vomiting and diarrhea) was dose-limiting. Two patients had possible neurological toxicity. Recommended doses for further studies are cisplatin 90 mg/m2 and cytosine arabinoside 900 mg/m2.