The aim of this study was to estimate to what degree malignant pleural mesotheliomas were reported as occupational cancers. The study included all malignant pleural mesotheliomas (n = 210) found in the Cancer Registry 1980-1989 from four Swedish counties. Whether or not a case was reported as occupational cancer was found in the Swedish Register of Reported Occupational Diseases. To evaluate the presence of exposure histories, the chest department files for 58 mesotheliomas from one county were reviewed. The reporting was low, with only 75 mesotheliomas (36%) reported. All the cases were men, and for the men, the reporting frequency was 42%. The reporting was significantly lower for the last part of the decade than for the first part. The reporting frequency decreased with age. In the review of the chest department files, an exposure history was found in 93% of the reported cases and in 47% of the unreported cases. It is concluded that physicians must give more priority to exposure histories in patients with pleural mesotheliomas.