This is an open label clinical trial of imatinib mesylate 800 mg po/day in a population of patients with unresectable, recurrent glioblastoma multiforme. Patients will be treated for up to 12 months

Inclusion Criteria:

1. Histologically documented diagnosis of GBM.
2. Immunohistochemical documentation of expression of PDGFR.
3. Unresectable, recurrent disease by MRI and spectroscopy

Exclusion Criteria:

1. Treatment with any other investigational agents within 28 days of first day of study drug dosing.
2. Concurrent chemotherapy.
3. Concurrent radiotherapy.

Other protocol-defined exclusion criteria may apply.