B. 33h, DATA FROM OCCUPATIONALLY EXPOSED PEOPLE Following a number of papers where an increased rate of leukaemia in radiologists, as compared to other medical practitioners, had already been re- ported [M25, M26, U13], in 1947 Dublin and Spiegelman [D8] published some preliminary data on United States physicians during the period 1938-1942, showing essentially that physicians experienced the same longevity and mortality as white males of the same age in the United States. No evidence of diseases as- sociated to radiation exposure was found in that study, but in a subsequent paper [D9] this research was extended to the mortality of medical specialists during the same period. Among 175.146 medical doctors listed in the American Medical Directory in 1940, 37.610 (or 21 per cent) were classified as full-time specialists. During the five years covered by the study there were 12.419 doc- tors dead in the age group 35-47 and 2.029 of these (or 16.3 per cent) were medical specialists. The mortality ratio from all causes of specialists was 78 per cent, taking the death rate of all physicians to be 100 per cent. Ra- diologists were reported to have a mortality ratio of 0.90, dermatologists of 0.98, pathologists of 0.60. Radiologists showed a high rate of mortality from cancer and leukaemia and among 95 recorded deaths of radiologists leukaemias were higher than in any other speciality. 335. In 1956 Warren [W2] reported on 82.441 physicians dead during the period 1930-1954 inclusive. He found that physicians had a mortality rate about the same as that of the general adult population. In 1950 in the United States the average age at death for white males having reached 25 years of age was 65.6 years. Radiologists died on the average 5.2 years earlier than other non- radiologist physicians, who died at 65.7 years. Also, the non-radiologists known to be exposed ro radiation did show some life-shortening (they lived on the average 63.7 years) although less than that of non-radiologists. Failla and McClement [F4] estimated that radiologists received an accumulated exposure that could vary from rather low values to about 1000 R, with a possible whole-body exposure of 500 R in 35 years of practice. 336. Warren [W2] found that deaths from leukaemia among physicians were 120 over the period 1950-1954, which rate was about three times that for the gene- ral adult population. During 1930-1954, 0.63 per cent of the deaths from specified causes occurring among non-irradiated physicians were due to leukaemia, against a 2.33 per cent among other specialists having had some contact with