The mortality experience of 33,833 US Army and Marine Corps Vietnam veterans who died during 1965-1988 was compared with that of 36,797 deceased non-Vietnam veterans using proportionate mortality ratios (PMRs). Military service information was abstracted from military personnel records and cause of death information recorded from death certificates. Army Vietnam veterans had statistically significant excesses of deaths from laryngeal cancer (PMR = 1.38) and lung cancer (PMR = 1.08). There was an excess of external causes (PMR = 1.03), including motor vehicle accidents (PMR = 1.03) and accidental poisonings (PMR = 1.17). In contrast to Army Vietnam veterans, the results for Marine Vietnam veterans varied according to the referent population used. When compared with non-Vietnam veterans, Marine Vietnam veterans had significantly elevated PMRs for lung cancer (PMR = 1.17) and skin cancer (PMR = 1.33). There was also a significant excess of external causes of death (PMR = 1.06), accidental poisonings (PMR = 1.19), and homicides (PMR = 1.16) compared with all non-Vietnam veterans.