Although recent efforts to advance the treatment of gliomas through radiotherapy and chemotherapy may seem to be a relatively new area of growth and development, these efforts have been in progress since the therapeutic potential of radiation therapy was discovered in the late 19th century. Cushing's use of brachytherapy has been mentioned several times in the literature without receiving an appropriate in-depth analysis. The reasoning behind Cushing's initial use of brachytherapy was not fully examined, and a close analysis of the outcomes of this therapy was not made. In addition, Cushing's use of his “radium bomb” occurred more commonly than the 3 cases previously documented. The authors reviewed all the patient records available at the Cushing Brain Tumor Registry—which represents the most complete series of patient records from the Cushing era—and selected those patients who underwent treatment with Cushing's “radium bomb.” The authors place these early attempts to optimize interstitial radiation of brain tumors in their historical perspective.