A 45-year-old man with suspected recurrent malignant glioma was evaluated by magnetic resonance imaging (MRI), positron emission tomography (PET) and 131I labeled monoclonal antibody G-22 (G-22) scan. Following Gadolinium-DTPA, a TI-weighted spin echo image (TR 500 msec, TE 20 msec) demonstrated a large mass with an irregular margin in the left temporo-parietal area. An 18F labeled fluorodeoxyglucose PET study demonstrated marked accumulations in the left temporo-parietal area. Serial 131I-G-22 scintigraphy was obtained for a week after the injection. The uptake was most increased on the 2nd day after the injection. 131I G-22 was specific for tumor-associated antigens.