In the largest iron and steel works in Japan, six cases of lung cancer had been found among coke oven workers from 1947 to 1971. Labour Standard Bureau of the Ministry of Labour organized a task group of specialists to conduct an investiga-tion whether these cases should be considered as occupational. This paper is an English version of the report submitted to Labour Standard Bureau from the task group.An epidemiological survey conducted by the Ministry of Labour indicated that lung cancer incidence among retired blast furnace coke oven workers in the iron and steel works exceeded that of the expected number calculated from the general Japanese male polulation and the relative frequency of lung cancer cases to malign-ant neoplasia of all sites also exceeded that of the expected number. The task group was not able to conduct research on coke manufacturing chemical companies and manufacturing (specialized) companies because the number of lung cancer cases was too small.