Glioblastoma is a highly malignant brain tumour that is almost always fatal within a few months or years. Standard treatments such as surgery, radiotherapy and chemotherapy appear to have reached their limits and are unable to prevent tumours from recurring. A fundamentally different approach is needed if we are to alter the course of this devastation disease. Two possibilities are explored: firstly, immunotherapy might be able to re-sensitise tumours that have become resistant to chemotherapy by eliminating drug-resistant cells. Secondly, the reason conventional treatment fails might be that glioblastomas contain ""cancer stem cells"" that are not only the main cells driving the tumour, but also possess unique properties that make them particularly resistant to radiation and chemotherapy. By acting through entirely different mechanisms, immunotherapy might succeed in attacking these cells where conventional treatments have failed.