Army Chemical Corps personnel who served in Vietnam were among those service personnel with the greatest potential for exposure to herbicides. An earlier evaluation of the mortality experience of 894 Army Chemical Corps Vietnam veterans found a statistically significant excess risk of dying from digestive disease, primarily due to cirrhosis of the liver, and from motor vehicle accidents. That study was expanded to include 2,872 Vietnam veterans who served with the Army Chemical Corps and a comparison cohort of 2,737 veterans who never served in Southeast Asia but who did serve in the same occupational category. The results of the analysis comparing the Vietnam cohort to the non-Vietnam cohort support the earlier finding of a significant excess of deaths from digestive diseases (adjusted relative risk (RR) 5 3.88, 95% C.I. 5 1.12-13.45) primarily due to liver cirrhosis. Non-significant elevated relative risks were observed for all cancers combined, digestive and respiratory systems cancers, skin cancer, lymphopoietic cancers, and respiratory system diseases. Compared to the mortality rates in the general population, the non-Vietnam Army Chemical Corps veterans had a statistically significant deficit in mortality from all causes combined, which is consistent with a 'healthy selection bias' seen among military populations (SMR 5 0.79, 95% C.I. 5 0.66-0.94). For the Vietnam veterans, patterns of elevated but nonsignificant SMRs persisted for diseases of the digestive and respiratory systems and for selected cancer sites. Am. J. Ind.