Use of a high energy linear accelerator (giving high dose rates) for whole body irradiation is recommended because (a) there is a shorter treatment time compared with other techniques using orthovoltage or 60Co irradiation; and (b) there is more comfort for the patient, who does not have to turn over to receive an acceptably uniform dose. Dosimetry indicates that the usual data is not applicable for such treatments given at large distances from the source. A method of dosage calculation at large distances was checked by using TLD dosimetry in a Rando phantom.