A retrospective cohort study of mortality was conducted to assess whether the military service of young Australian men in Vietnam has influenced their overall death rates, or those from specific causes. The study was of all national servicemen who were conscripted during the conflict and served in the Army for at least 12 months. Of these, 19 205 served in Vietnam (veterans) while 25 677 served only in Australia (non-veterans). These men were traced from the end of their national service (between 1966 and 1973) until the beginning of 1982. For most causes of death, the observed number of deaths of veterans and of non-veterans was less than expected from Australian population death rates, and for no cause was there a statistically significant excess of deaths compared with that of the Australian population. Similarly, when veterans were compared with non-veterans, there was no statistically significant difference in deaths for all causes combined, for diseases of the circulatory system, for deaths in motor vehicle accidents, for suicide and for all external causes after adjustment for the different subsequent death rates of men who had served in different Army corps. All seven deaths from diseases of the digestive system were of veterans. There was no excess of deaths among veterans from cancer or from atypical causes of death in this group of young men. Three-quarters of deaths of both veterans and non-veterans were from external causes, often involving motor vehicle accidents.