Adenovirus-mediated gene transfer of interferon gamma (AdIFN) elicits rejection of intracerebral Lewis lung carcinoma. In this system, gene transfer into brain parenchymal cells is both necessary and sufficient to generate the antitumor response. Despite persistent parenchymal inflammation and demyelination, wild-type mice injected intracerebrally with either AdIFN or ␤-galactosidase adenovirus (AdBGAL) perform as well as non-injected animals in behavioral, memory, and motor tests. Both AdIFN and