A person-years at risk life-table analysis system of computer programs has been developed by the National Institute for Occupational Safety and Health (NIOSH) and is available with detailed documentation. The system was specifically designed to analyze occupational cohort mortality data. These programs require more computer core space and processing time than other available life-table programs. However, the NIOSH programs are advantageous because they include the following: (1) input data editing and modification, (2) mortality rates for 89 cause-of-death categories, (3) assignment of cumulative doses to specific person-years based on either personal or area exposure data, and (4) simultaneous examination of observed and expected deaths by duration of employment (or dose), latency, age, and calendar time.