To complicate matters further, there was no central listing of participants by name. A study cohort was finally identified from research by the Armed Forces Radiobiology Research Institute (AFRRI), an element of the Defense Nuclear Agency. The list named 3,153 military personnel* who had been issued film badges at the Nevada Test Site (NTS) for the period that included 31 August 1957, the date of Shot SMOKY. Seventy-one names were added from other sources, thereby making a total cohort of 3,224 individuals. This number of individuals was used in the study. Several sources were then explored to identify the cases of leukemia and other cancers among this cohort. Four leukemia cases were identified from a list of more than 3,000 individuals who made inquiries regarding the publicity surrounding the index case. 31 August 1957. Of these personnel, 447 had been at the NTS on The AFRRI list was also compared with various clinical files, including those of the Armed Forces Institute of Pathology (AFIP), the Veterans Administration (VA) death benefit file, and personnel records at the National Personnel Records Center. Four more cases were identified from these records, which made a total of nine (including the index case). Each case was confirmed by CDC, and the total exceeded the expected incidence of 3.5 leukemia cases in this cohort. The expected incidence was calculated by applying age- and sex-specific incidence rates published by the National Cancer Institute to the person-years accumulated by the SMOKY cohort from 1957 through mid-1977. the study. Eight of the nine cases had died by the time of This exceeded the expected mortality of 2.9 calculated from U.S. rates for the 1970s. Both comparisons were considered statistically signif- icant, even if two of the cases that could be questioned with regard to inclusion in the cohort were dropped. Radiation exposure was considered as a possible cause of this increased incidence. The available dosimetry (film badge results) and radiological analyses of tissue from two patients did not, however, support this hypothesis. Therefore, CDC tentatively concluded that if the apparent excess of *Primarily U.S. Army personnel who were assigned to Exercise Desert Rock and wore film badges provided by the U.S. Army Signal Depot, Lexington, KY. 182