Objectives To present current, nationally representative US findings on the past-year and lifetime prevalences, sociodemographic correlates, psychiatric comorbidity, associated disability, and treatment of DSM-5 posttraumatic stress disorder (PTSD). Methods Face-to-face interviews with 36,309 adults in the 2012–2013 National Epidemiologic Survey on Alcohol and Related Conditions-III. PTSD, alcohol and drug use disorders, and selected mood, anxiety, and personality disorders were assessed using the Alcohol Use Disorder and Associated Disabilities Interview Schedule-5. Results Past-year and lifetime prevalences were 4.7 and 6.1 %, higher for female, white, Native American, younger, and previously married respondents, those with <high school education and lower incomes, and rural residents. PTSD was significantly associated with a broad range of substance use, mood, anxiety, and personality disorders, and past-month disability. Among respondents with lifetime PTSD, 59.4 % sought treatment; an average of 4.5 years elapsed from disorder onset to first treatment. Conclusions DSM-5 PTSD is prevalent, highly comorbid, disabling, and associated with delayed help seeking. Additional research is needed to elucidate relationships identified herein, estimate PTSD-related costs, investigate hypotheses regarding etiology, course, and treatment, and support decisions about resource allocation to service delivery and research. Initiatives are needed to destigmatize PTSD, educate the public about its treatment, and encourage affected individuals to seek help.