The Worker Exposure Surveillance System (WESS) is an integrated computer hardware and software system for monitoring potential exposures to workers. The monitoring system is comprised of bar cod scanning devices, local or centralized data storage units, and a data management tool. The first WESS system was implemented at the Department of Energy Y-12 Plant in Oak Ridge, Tennessee as a pilot project conducted by Oak Ridge Associated Universities, Center for Epidemiologic Research for the U.S. Centers for Disease Control and Prevention. Specifically, the WESS pilot project at Y-12 included five scanning stations, each consisting of a bar code reader attached locally to a stand alone personal computer, and a sixth PC located at the ORAU/CER site. Data from the scanning stations were periodically collected and transferred to the sixth PC where the WESS database and Data Management Application resided. The WESS scanning stations collect primary data necessary to continuously monitor worker/work area relationships. Each time a worker enters or exits a work area controlled by a WESS scanning station, the worker's badge is presented to the scanner, resulting in a record being generated that includes the worker's badge number, work area number, date and time of entry or exit, and the identity of the recorded as an entry (I) or exit (O) record. Once collected at the scanning stations, theses records are transferred to a centralized PC where the records are stored in a Microsoft Access 95 database. A number of demographic attributes are added to the WESS database for workers previously unmonitored. Potential exposure information, chemicals or physical agents designated for each monitored location, also resides in the WESS database and can be linked to the scanning records via location, date, and date range. At this point, these records are available to the authorized user through the WESS Data Management Application.