Australian male Vietnam veterans (N = 388) were assessed 22 and 36 years after their return to Australia using standardized diagnostic interviews, with added data from Army records and self-report questionnaires. Among veterans who ever had posttraumatic stress disorder (PTSD), 50.3% had a current diagnosis at the second assessment; of those who had a current diagnosis at Wave 1, 46.9% were also current at Wave 2. Late onset occurred for 19.0% of veterans, of whom 60.8% were current at Wave 2. Multivariate analysis compared veterans with no history of PTSD (n = 231) with veterans who had ever had PTSD (n = 157) to assess risk factors for PTSD incidence; and veterans with a history, but not current PTSD (n = 78) with veterans who had current PTSD at the second assessment (n = 79) to assess risk factors for failure to remit. Incidence was associated with lower education, shorter Army training predeployment, higher combat, excess drinking, and help-seeking after return to Australia. Prevalence was associated with having a father who saw combat in World War II, being injured in battle, having a lower intelligence test score, experiencing higher combat, and having a diagnosis of phobia at the first assessment. Only combat was common to incidence and prevalence.