A collaborative study has been performed in order to detect cases of pleural mesothelioma diagnosed or treated in Italy in the years 1984-88. Cases have been notified to ISS by 88 centres (clinics of thoracic surgery and respiratory diseases, oncologic centres, institutes of pathology), active in 14 Italian regions. Altogether, 575 cases (415 males and 160 females) have been included in the study. Information on occupation and/or on non occupational exposure to asbestos was available for 65% of the subjects, and the occurrence of definite or possible exposure to asbestos was estimated for 58% of them.