THERAPEUTIC IRRADIATION of the entire body was first employed in the hope that it would devitalize or destroy all wandering malignant cells or early metastatic foci without harm to the patient. Of course, much research on animals preceded the use of this technique on human beings. Total body irradiation, however, requires unique equipment. There are presently at least three specially designed installations for whole body irradiation in the United States. The earliest facility is at the Navy Medical Research Institute, Bethesda, Maryland. The irradiation agent we use is cobalt60.