For many years there has been prevalent an impression of a possible relationship between exposure to radiation and the subsequent development of leukemia. As early as 1911 there appeared the first report on the matter by von Jagic and coworkers (1), in which a brief statement—based in part on hearsay—is made concerning the occurrence of leukemia in four persons who had experienced prolonged exposure to radiation. Of only one of these cases did the authors have any personal knowledge. Since that time there have appeared perhaps a dozen reports on the specific subject of the development of leukemia in persons non-therapeutically exposed to small doses of radiation over prolonged periods. Twenty-three cases have been recorded in the literature, including the four by von Jagic. In a few of the cases details are lacking and the relationship is not well established. In 1912 Aubertin (2) referred to a case of myeloid leukemia discovered in a French radiologist and followed by Vaquez. In 1924 Carman and Miller (3...