Alcohol and tobacco habits have been identified as strong risk factors for esophageal cancer. Increased risks of esophageal cancer have also been reported to be associated with occupational exposure to asbestos and various metals, among vulcanization workers, asphalt workers, and workers in the petrochemical industry. Mortality and cancer incidence were investigated in a series of studies of workers exposed to combustion by-products, i.e., chimney sweeps, waste incinerator workers, gas workers, and bus garage workers exposed to diesel exhausts. The SMRs for esophageal cancer ranged from 150-386 in these cohorts, and a combined SMR of 289 (95% C.I. 174-452) was obtained. Available data on smoking habits and indirect indicators of alcohol consumption show that the excess cannot be attributed solely to these factors. It seems likely that occupational exposure to combustion products is associated with an increased risk of esophageal cancer.