OUTLINE: This is a dose escalation study of irinotecan. Patients receive irinotecan IV over 90 minutes weekly on weeks 1-4 and carmustine IV over 1 hour on weeks 1-6. Treatment continues in the absence of disease progression or unacceptable toxicity. Cohorts of 3-6 patients receive escalating doses of irinotecan until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose at which no more than 1 of 6 patients experiences dose limiting toxicities.