Despite years of intensive research, the prognosis of high-grade gliomas (HGG) remains poor, as these tumors are highly resistant to currently available therapies. Therefore, there is a need for the development of new therapeutic strategies, such as the use of monoclonal antibodies (MoAbs) in association with radioisotopes, in order to achieve better responses and prognosis. This article describes our experience in radioimmunotherapy (RIT) with MoAbs and tumor pre-targeting with the avidin-biotin system, either in systemic or locoregional administrations. This therapy offers the exciting prospect of increasing the specificity of tumor cell irradiation with radioisotopes. We suggest that RIT, both systemic and locoregional, should be used as part of a combined modality approach: in combination with surgery, radiotherapy and chemotherapy.