Although prognosis of malignant gliomas did not change dramatically for the last 15 years, tumorigenesis is much better understood. The study of the genetic alterations occurring in these tumors allowed to recognise the most critical genes involved, which are either overexpressed oncogene, or inactivated tumor suppressor gene. Gene therapy is a natural outcome of such progresses. One way of tumor gene therapy is based on correction of genetic defect either by introducing the missing tumor suppressor gene or by blocking overexpression of an activated oncogene. Alternatively, "destructive" gene therapy is based on a "suicide" gene introduced in tumor cells. These approach results now in phase 1 protocol.