Occupational exposure to asbestos is associated with malignant tumors in the lung and malignant mesothelioma in the pleura and peritoneum. Tumors at other sites have also been reported. The benign asbestos-related disorders are asbestosis and pleural fibrosis, effusion and plaques. Chronic bronchitis may be associated with previous asbestos exposure. Fiber dimensions and durability are main factors for carcinogenicity. For practical reasons, long and thin fibers like asbestos should be considered carcinogenic. The diagnosis of asbestos-related disease is based upon information on occupational exposure. Analysis of lung fiber burden supports information given by the occupational history and gives valuable information on dose-response and dose-effect relationships. Building materials with good maintainance of the surfaces do not release asbestos fibers, whereas materials subject to mechanical stress should be replaced by nonasbestos-containing materials to avoid the stipulated very low increase in cancer risk.