During the production of coke, large quantities of coke oven gas are emitted. People who work on the top or on the sides of coke ovens are exposed to this oven gas, which contains a range of carcinogenic chemicals. To investigate the cancer risks under these work conditions, a retrospective study was undertaken. In total 11,399 former workers were enrolled in the study. Of these, 5639 had worked in the coke plant for at least six months between 1945 and 1969. The other 5740 had worked in another plant during the same period and formed a non-exposed group for comparison. The study group was followed up until 1984 for mortality. The causes of death were obtained from the Central Bureau of Statistics. Among the coke oven workers significantly higher death rates were found for lung cancer and non-malignant respiratory disease. Mortality in the byproduct section was similar to that expected. Among workers in the tar distillery the rate for lung cancer was higher than expected. The risk for gastric cancer and non-malignant respiratory disease among the workers of the coke shipping department was increased but the SMRs did not reach statistical significance. No data were collected about individual smoking habits or socioeconomic state of the study subjects and the possibility that the risk found could be attributed to these factors cannot be ruled out. It has been stated by other investigators, however, that the effect of not controlling for smoking tends to be modest.