It has been shown that neuroblastoma can be controlled by irradiation even after extensive spread. It must be agreed that in some instances it is highly unlikely that cancerocidal doses could have reached all the tumor cells. With the knowledge that this tumor may occasionally spontaneously regress or mature into a benign ganglioneuroma, it may be postulated that irradiation can promote or accelerate the process of maturation. To our knowledge there have been no follow-up histological studies in cured individuals. This would be of great value if biopsy of the liver or other previously involved organs could be made perfectly safe. The report of patients showing arrest and regression of disease after chemotherapy should also stimulate further interest in tile biological behavior of this unusual tumor. Unquestionably, radiation does arrest and control this disease by direct cancerocidal action. However, the favorable results in a few instances of disseminated neoplasm render further clinical investigations highly important in solving the riddle of its biological behavior.