This phase I study evaluated a Gene Mediated Cytotoxic Immunotherapy approach for malignant gliomas, including glioblastoma multiforme and anaplastic astrocytoma. The purpose of this study was to assess the safety and feasibility of delivering an experimental approach called GliAtak which uses AdV-tk, an adenoviral vector containing the Herpes Simplex thymidine kinase gene, plus an oral anti-herpetic prodrug, valacyclovir, in combination with standard of care radiation.