The first step in the data reduction process is to create the "working files" (see Figure A1 ) for the sub-cohort of X-10/Y-12 white males that are free of critical errors (see CEDR documentation for Demographic Analysis File) . These files were needed to deal with combined data for individuals employed at more than one facility. The Demographic and Internal Exposure file contains demographic data, and a yearly value that indicates the facility of employment, with a special value being assigned when a person worked at more than one facility. Facility was lagged in all analyses and for years when a person had internal exposure data from more than one facility, the data were combined by retaining the highest value for that year. A special variable to identify workers employed at TEC before being employed at X-10 or Y-12 was created. We have assumed that these individuals have no external exposure but that many of them have internal exposure and will enter follow-up classified as internal exposed workers . The Cumulative External Dose file contains yearly cumulative external dose (with a two, ten, or twenty year lag) data from all previous years of employment at all Oak Ridge facilities.