THE Meyerstein Institute of Radio-Therapy at the Middlesex Hospital, London, was opened by Sir William Bragg on June 9, before a large audience with many representatives of medicine and science. Sir William Bragg referred in reminiscent terms to the early days of X-rays and radioactivity, pointing out the ever-growing interest in the quest of the invisible phenomena about us. The Institute which he declared open is at the north end of the original Cancer Wing of the Hospital, four floors of which have been reconstructed and adapted to radiological work. The main equipment consists of four X-ray installations having Metropolitan-Vickers tubes actuated at 250 kilovolts, four Newton and Wright sets of oil-cooled Siemens tubes to be run at 200 kilovolts, and a 4-gram radium unit, the radium being automatically transferred to a large radium safe surrounded by 10 inches of lead when not in actual use upon patients. The protection of the personnel has been carefully studied throughout the entire working arrangements. The layout of the Institute is of a very pleasing as well as efficient character, being well ventilated and lighted, with ample space and air for patient and operator alike. The whole policy has been to provide trustworthy apparatus with the best possible conditions under which a selected staff can pursue radiological investigation.