The information on occupations obtained in Finland's 1970 census was linked with the files of the Finnish Cancer Registry from 1971 through 1980 in order to establish the occupational group-specific relative risks (RR) of lung cancer. The distribution of lung cancers into histologic types varied with the age of the patients at the time of diagnosis. When 38 high-risk occupational groups were combined, the age-specific distribution of lung cancer into histologic types did not differ significantly from the corresponding distribution for other economically active men. Of individual occupational groups, young farmers had a higher RR of small cell carcinoma than older farmers or other economically active young men. Besides their high overall lung cancer risk, miners and quarriers had a very high risk of small cell carcinoma as compared with other economically active men. Servicemen and repairmen in the metal industry had a high risk of epidermoid carcinoma. Welders had a high risk of epidermoid carcinoma, but their risk of small cell carcinoma was lower than expected. There were no other excess risks of any histologic type of lung cancer attributable to occupational factors.