Treosulfan is a bifunctional alkylating prodrug with activity against various solid tumors. To improve the outcome for patients with recurrent malignant glioma, we assessed the efficacy of intravenous treosulfan (6-10 g/m2 4-weekly) as salvage therapy for patients with recurrent or progressive glioblastoma (GB, n = 14) or anaplastic astrocytoma (AA, n = 2). All patients had prior involved-field radiotherapy and adjuvant nitrosourea-based chemotherapy. A total of 56 cycles were administered. Tumor responses were assessed radiologically and clinically prior to each cycle. All patients were assessable for toxicity, response and survival. There were no complete or partial responses (CR, PR). Two patients progressed after the first cycle, 14 patients had initially stable disease (SD). Median progression-free survival was 3.25 months for the GB patients. Five patients were progression-free at 6 months (30%), including the 2 AA patients. The 2 AA patients are stable at 22 months. Myelosuppression was the dose-limiting toxicity in this cohort of nitrosourea-pretreated patients. Treosulfan has modest activity in patients with recurrent malignant glioma. Further evaluation of treosulfan in chemonaive malignant glioma patients is warranted.