In 1978, the National Institute for Occupational Safety and Health (NIOSH) undertook a study of 25,000, civilian employees of the Quincy Naval Shipyard. The cohort consisted of white males who worked at the shipyard from 1952-1977 who were identified from health records from the shipyard’s health center. Review of records revealed that 1,000 cancers occurred during this period. Beginning in 1978, the 18,000 study members that were still alive and could be located were mailed annual questionnaires. This follow-up will continue until 2010. What kind of cohort study is this? PROSPECTIVE? RETROSPECTIVE? AMBIDIRECTIONAL?