The occurrence of malignant pleural mesothelioma (MT) is a sentinel event in occupational and environmental medicine. The association of pleural MT and asbestos exposure is well documented and it is well known that no threshold can be demonstrated below which there is no risk of developing MT. During the period 1994-1998, 3 patients were referred from the Pneumology Division to the Occupational Medicine Department of the Spedali Civili in Brescia. They had MT and they had a peculiar asbestos exposure. A thorough occupational and environmental history was taken by means of a standardized questionnaire. The first patient was environmentally exposed to crocidolite when she lived near an asbestos mine in Australia. The second was a teacher and the third was a goldsmith and both were occupationally exposed to asbestos. The case descriptions revealed the importance of a standardized evaluation of occupational and environmental exposure to asbestos. In this way otherwise ignored asbestos exposures can be identified therefore avoiding an underestimation of MT attributable to asbestos. The role of the occupational physician, both in hospital referrals and while taking standardized histories, is also stressed along with the importance of this contribution on the one hand to the epidemiological recording of sentinel events and on the other to the etiological definition of the cases, which was in fact our principal aim.