BEFORE beginning my paper I wish to take the opportunity to express my appreciation of the honor extended to me in having been asked to deliver a paper before so distinguished a society. It was only with reluctance that I accepted the invitation, for I have nothing new or startling to present to you. However, I will try to describe to you the methods which we have found of practical value in the treatment of malignant disease at the State Institute at Buffalo. 1. Theories of Action Let us first consider briefly the theories of action. These may be summarized as: (1)Ionization, photochemical, or physical theory. This hypothesis assumes the collision of rays with the atomic cell structure, resulting in the formation of beta and secondary gamma rays and, perhaps, some unknown biochemical modification of the protoplasm. (2)Thermochemical action, as exemplified by the point heat theory of Dessauer. (3)Discharge action in which absorbed radiation serves to neutralize or discharge excessive accumulated tissue ch...