A retrospective study was carried out of mortality among United States chemical workers assigned to the production of substances contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (1746016) (TCDD) with particular interest being paid to the role of this agent in the development of soft tissue sarcoma, Hodgkin's disease, non Hodgkin's lymphoma, stomach cancer, nasal cancer, and cancer of the liver. Male workers from 12 companies were included in the study for a total of 5172 individuals. The results of this study found little increase in mortality from the cancers associated with TCDD in previous studies of humans, with the exception of soft tissue sarcomas. Mortality from cancers of the trachea, bronchus, and lung was nonsignificantly higher in the cohort. Among workers with 20 years or more of latency, mortality from respiratory cancer was significantly increased in the high exposure subcohort which had 1 year or more of exposure, but not in the subcohort with less than 1 year of exposure. There was a small but significant increase in mortality from all cancers combined, being 15% higher than expected in the overall cohort. The subcohort with 1 year or more of exposure and 20 years or more of latency had a 46% increase in all cancers combined and a 42% increase in cancers of the respiratory tract. The authors conclude that the increased mortality, particularly in the subcohort with 1 year or more of exposure, is consistent with the status of TCDD as a carcinogen.