This is a combination Phase I/Phase II trial of CPT-11 in patients with refractory gliomas. The study drug inhibits topoisomerase I, a nuclear enzyme involved in DNA replication. Preclinical studies indicate a sensitivity of glioma cells to CPT-11, therefore, after establishing toxicities and maximum tolerated dosages, the efficacy of the drug will be determined. As an outcome measure, topoisomerase I levels in brain tumor tissue will be correlated with response.