This observational study ( historical cohort) is the second phase of a study of the mortality of workers employed between 1943 and 1985 at the federal nuclear plants in Oak Ridge, Tenn. The first phase was limited to white males who were employed only during the World War II era when radiation monitoring programs were being developed.

1. To extend the evaluation of the health effects of employment in the nuclear industry in Oak Ridge to include Oak Ridge workers who were omitted from earlier studies;

2. to compare the mortality experience among the facilities;

3. to carry out dose-response analyses for those individuals who were potentially exposed to external radiation; and

4. to address methodological problems that occur when individuals employed at more than one facility are included in the analyses.

This study was initiated out of the need to develop statistical methods for combining mortality data from multiple nuclear facilities. Historically, there were major differences between facilities in terms of when they opened, the kind and frequency of monitoring for radiation exposures, etc. The data from the different facilities were combined to fully utilize all available information concerning the potential adverse health effects related to working at these facilities.