Six patients with optic pathway gliomas who were previously managed with surgery and/or chemotherapy were treated with carboplatin (560 mg/sq m) after radiographic evidence of disease progression. The median age at diagnosis was 2 years (range 4 months to 7 years), and the interval between diagnosis and carboplatin therapy ranged between 7 months and 6.5 years (median 1.8 years). Treatment was given at 4-week intervals and continued until unacceptable toxicity supervened, the disease progressed, or the disease was stable for 12 months. All patients demonstrated disease stability at the outset of the third cycle and continued to do so at the time of this writing. Two patients are 16 and 32 months from initial carboplatin therapy and have been off treatment for 5 and 14 months, respectively; two patients are still receiving therapy at 7 and 11 months after their initial treatment. During the study, two patients developed hypersensitivity to the drug, requiring its discontinuation. Toxicity was minimal, consisting mainly of thrombocytopenia, requiring a one-dose reduction in four of the six treated patients. No platelet transfusions were needed. These results suggest that carboplatin can arrest growth of progressive optic pathway gliomas in children and can allow delay of radiotherapy. A larger trial will be required to define the optimal use of carboplatin in the treatment of low-grade gliomas in children.