The Vietnam Era Health Retrospective Observational Study (VE-HEROeS) is a national study on the health and well-being of Vietnam Veterans, including Blue Water Navy Veterans, as well as Veterans who served elsewhere during the Vietnam Era (1961-1975), and similarly aged U.S. residents who never served in the military. The investigators will invite approximately 43,000 Vietnam and Vietnam Era Veterans, and approximately 11,000 members of the general U.S. population to participate in VE-HEROeS. These individuals are scientifically selected to participate; the study is not able to accept volunteers.