A number of chemicals encountered predominantly in occupational settings have been causally linked with cancer in humans; furthermore, several industrial processes and occupations have been associated convincingly with increased rates of cancer, although the specific carcinogens remain to be identified. The tissues affected are mainly the epithelial lining of the respiratory organs (nasal cavity, paranasal sinuses, larynx and lung), and urinary tract (renal parenchyma, renal pelvis and urinary bladder), the mesothelial linings, the bone marrow and the liver. During the period 1970-84, almost 4 million people (3.7 million men and 0.2 million women) in the Nordic countries were potentially exposed to above-average levels of one or more verified industrial carcinogens. It is expected that these exposures will result in a total of about 1,900 new cases of cancer every year in the Nordic countries around the year 2000, with 1,890 among men and fewer than 25 among women. The proportions that could be avoided if industrial carcinogens were eliminated would be 70% of mesotheliomas, 20% of cancers of the nasal cavity and sinuses, 12% of lung cancers, 5% of laryngeal cancers, 2% of urinary bladder cancers, 1% of the leukaemias, and 1% of renal cancers. Overall, it is estimated that verified industrial carcinogens will account for approximately 3% of all cancers in men and less than 0.1% of all cancers in women in the Nordic countries around the year 2000. No attempt was made to estimate the potential effects of suspected carcinogens in the workplace.