Gallium 68 is a positron-emitting radioisotope with a half-life of 68 minutes. It is easily prepared in the form of gallium edetate68Ga (68Ga-EDTA) from a long-lasting germanium-gallium cow. This tracer compound accumlates in most brain tumors and, using the positron form of the scintillation camera, pictures of the distribution of this radioisotope in the patient's head can be obtained. The lesions appear as an area of increased uptake of the radioisotope. In a series of 96 carefully observed patients, 41 cases with subsequently proved abnormalities were accurately diagnosed by this method. Nine cases with abnormalities were missed. Low radiation hazard to the patient, ease of preparation, and constant availability of the tracer compound at low cost make this radioisotope an excellent tracer for localizing brain tumors in conjunction with the positron scintillation camera.