ABSTRACT: IMPORTANCE:Many Vietnam-era women veterans served in or near war zones and may have experienced stressful or traumatic events during their service. Although posttraumatic stress disorder (PTSD) is well studied among men who served in Vietnam, no major epidemiologic investigation of PTSD among women has been performed. OBJECTIVES:To assess (1) the onset and prevalence of lifetime and current PTSD for women who served during the Vietnam era, stratified by wartime location (Vietnam, near Vietnam, or the United States), and (2) the extent to which wartime location was associated with PTSD, with adjustment for demographics, service characteristics, and wartime exposures. DESIGN, SETTING, AND PARTICIPANTS:Survey of 8742 women who were active-duty military personnel in the US Armed Forces at any time from July 4, 1965, through March 28, 1973, and alive as of survey receipt as part of Department of Veterans Affairs Cooperative Study 579, HealthVIEWS. Data were obtained from mailed and telephone surveys from May 16, 2011, through August 5, 2012, and analyzed from June 26, 2013, through July 30, 2015. MAIN OUTCOMES AND MEASURES:Lifetime and current PTSD as measured by the PTSD module of the Composite International Diagnostic Interview, version 3.0; onset of PTSD; and wartime experiences as measured by the Women's Wartime Exposure Scale-Revised. RESULTS:Among the 4219 women (48.3%) who completed the survey and a telephone interview, the weighted prevalence (95% CI) of lifetime PTSD was 20.1% (18.3%-21.8%), 11.5% (9.1%-13.9%), and 14.1% (12.4%-15.8%) for the Vietnam, near-Vietnam, and US cohorts, respectively. The weighted prevalence (95% CI) of current PTSD was 15.9% (14.3%-17.5%), 8.1% (6.0%-10.2%), and 9.1% (7.7%-10.5%) for the 3 cohorts, respectively. Few cases of PTSD among the Vietnam or near-Vietnam cohorts were attributable to premilitary onset (weighted prevalence, 2.9% [95% CI, 2.2%-3.7%] and 2.9% [95% CI, 1.7%-4.2%], respectively). Unadjusted models for lifetime and current PTSD indicated that women who served in Vietnam were more likely to meet PTSD criteria than women who mainly served in the United States (odds ratio [OR] for lifetime PTSD, 1.53 [95% CI, 1.28-1.83]; OR for current PTSD, 1.89 [95% CI, 1.53-2.33]). When we adjusted for wartime exposures, serving in Vietnam or near Vietnam did not increase the odds of having current PTSD (adjusted ORs, 1.05 [95% CI, 0.75-1.46] and 0.77 [95% CI, 0.52-1.14], respectively). CONCLUSIONS AND RELEVANCE:The prevalence of PTSD for the Vietnam cohort was higher than previously documented. Vietnam service significantly increased the odds of PTSD relative to US service; this effect appears to be associated with wartime exposures, especially sexual discrimination or harassment and job performance pressures. Results suggest long-lasting mental health effects of Vietnam-era service among women veterans.