The long-term health consequences of war service remain unclear, despite burgeoning scientific interest. A longitudinal cohort study of a random sample of Australian Vietnam veterans was designed to assess veterans' postwar physical and mental health 36 years after the war (2005-2006) and to examine its relation to Army service, combat, and post-traumatic stress disorder (PTSD) assessed 14 years previously (1990-1993). Prevalences in veterans (n = 450) were compared with those in the Australian general population. Veterans' Army service and data from the first assessments were evaluated using multivariate logistic regression prediction modeling. Veterans' general health and some health risk factors were poorer and medical consultation rates were higher than Australian population expectations. Of 67 long-term conditions, the prevalences of 47 were higher and the prevalences of 4 were lower when compared with population expectations. Half of all veterans took some form of medication for mental well-being. The prevalence of psychiatric diagnoses exceeded Australian population expectations. Military and war service characteristics and age were the most frequent predictors of physical health endpoints, while PTSD was most strongly associated with psychiatric diagnoses. Draftees had better physical health than regular enlistees but no better mental health. Army service and war-related PTSD are associated with risk of illness in later life among Australian Vietnam veterans.