Because Vietnam veterans comprise the majority of all living veterans and most are now older adults, the urgency and potential value of studying the long-term health effects of service in the Vietnam War, including effects on mortality, is increasing. The present study is the first prospective mortality assessment of a representative sample of Vietnam veterans. We used one of the longest follow-up periods to date (spanning older adulthood) and conducted one of the most comprehensive assessments of potential risk factors. Vital status and cause of death were ascertained for the 1,632 veterans who fought in the Vietnam theater (hereafter referred to as theater veterans) and for 716 Vietnam War–era veterans (hereafter referred to as era veterans) who participated in the National Vietnam Veterans Readjustment Study (1987–2011). As of April 2011, 16.0% (95% confidence interval: 13.1, 19.0) of all Vietnam veterans who were alive in the 1980s were deceased. Male theater veterans with a high probability of posttraumatic stress disorder (PTSD) were nearly 2 times more likely to have died than were those without PTSD, even after adjustment for sociodemographic and other characteristics. A high level of exposure to war zone stress was independently associated with mortality for both male and female theater veterans after adjustment for sociodemographic characteristics, PTSD, and physical comorbid conditions. Theater veterans with a high level of exposure to war zone stress and a high probability of PTSD had the greatest mortality risk (adjusted hazard ratio = 2.34, 95% confidence interval: 1.24, 4.43).