Locoregional radioimmunotherapy (LR-RIT) was administered to 111 patients (20 were recruited in a phase I and 91 in a phase II study) with malignant gliomas: 1 patient with oligodendroglioma, 7 patients with anaplastic oligodendroglioma, 2 with grade II astrocytoma, 10 with anaplastic astrocytoma and 91 with glioblastoma, amounting to 58 newly diagnosed and 53 recurrent tumours. The 131I-labelled monoclonal antibodies BC-2 and BC-4 were used in order to recognize stromal and intracellular glycoprotein tenascin, an antigen present particularly in glioblastoma. The patients were enrolled between February 1990 and December 1997 after conventional therapy. The radiopharmaceutical was injected directly into the tumour site. Sequential scintigraphies demonstrated a high and enduring uptake in the tumour. The mean irradiation dose in the tumour was 300 Gy per cycle. In the group of 74 phase II glioblastoma patients the clinical responses were as follows: 10 patients with stable disease (SD), 9 with partial responses (PR), 23 with no evidence of disease (NED) and 1 patient with complete response (CR). The median survival was 19 months. The response rate (CR + PR + NED) was 17.8% for those patients with bulky lesions, with a median survival of 17 months, but 66.6% for patients with small lesions, with a median survival of 25 months. Better outcomes were recorded in cases with less aggressive diseases: oligodendroglioma, anaplastic oligodendroglioma and anaplastic astrocytoma. We conclude that fractionated LR-RIT can be safely performed, with promising results especially in patients with minimal disease.