To test the hypothesis that occupational exposure to chemical agents-particularly organic solvents in certain industries-may cause primary liver cancer (PLC), a nested case-control study of PLC cases from the Danish Cancer Registry and an age- and sex-stratified random sample of controls from the Central Population Register in Denmark were linked with files of a national supplementary pension fund. Employment histories since April 1964 were obtained for 973 cases histologically classified as hepatocellular carcinoma, cholangiocarcinoma, or combined hepatocellular and cholangiocarcinoma and 15,348 controls. Men from 35 different industrial branches, women from 7 branches, and both men and women from 3 branches had an excess risk of PLC, with an odds ratio of (OR) > 1.0; 29 branches had an OR of liver cancer in excess of 3.0. Women from bookprinting and offset printing industries had an OR above 10. Only male farmers had an OR below unity (0.41). Employees from breweries, restaurants, hotels, motels, and distilleries had an increased OR of both PLC and esophageal cancer.