It is being slowly recognized that there is serious under-reporting of cancers that are occupationally related, in the sense that they would not have occurred without the occupational exposure. Data from the Workers' Compensation Boards of New South Wales in Australia and British Columbia in Canada relating to disease attributable to asbestos exposure indicate that in both jurisdictions the ratio of lung cancer cases to mesothelioma cases is much lower than epidemiological studies indicate must be occurring. Over the period from 1980 to 1994, if both jurisdictions are considered together, about 1,207 cases of lung cancer that would not have occurred without asbestos exposure went unrecognized as occupationally related. The data also suggest that it is unlikely that radiological asbestosis should be regarded as a necessary condition for there to be an increased risk of lung cancer following asbestos exposure.