A mortality study of 364 subjects identified as working at a 1,3- butadiene (106990) unit of Union Carbide was conducted. Of this cohort, 277 worked at the Rubber Reserve unit which produced butadiene from ethanol (64175), and 87 at units which produced butadiene from olefin cracking. As of December 31, 1990, 176 were alive, 185 were deceased, and three were of unknown status. The standardized mortality ratio (SMR) for death from all causes was 0.91. The SMR for deaths from all cancers was 1.05. The SMR for lymphosarcoma and reticulosarcoma was significantly elevated at 5.77 with four occurrences. Three of these four deaths occurred after more than 2 years exposure and 30 years latency. Additional information concerning these four individuals, including age at death, length of exposure, time from exposure to death, butadiene department and other exposures, was presented. A nonsignificant excess of stomach cancer deaths was detected. The incidence was more pronounced for subjects working at the Rubber Reserve unit for more than 2 years. Five cases were reported, giving a SMR of 6.57. Additional work history information on these individuals was provided. The authors conclude that butadiene is carcinogenic in humans, having contributed to an excess of mortality from lymphosarcoma and reticulosarcoma.