Approximately 19,000 cases of mesothelioma and 55,000 cases of lung cancer will arise in U.S. men with histories of nontrivial occupational exposure to asbestos. There are approximately 65,000 U.S. men now alive with clinically diagnosable asbestosis. These estimates are based, in the case of the cancer, on estimates of the effective number of asbestos-exposed workers required to produce the current national incidence of mesothelioma. The asbestosis estimates are based on a number of rough measures relating the prevalence of asbestosis to the incidence of mesothelioma, the incidence of compensable asbestosis in other countries, the prevalence of and mortality from pneumoconioses generally, and the number of workers heavily exposed to asbestos.