Using register data, time trends in mesothelioma incidence in Australia from 1945 to 2002 were calculated. Incidences are reported by age, sex, anatomic site, and state of notification. Associations with occupational and environmental asbestos exposure histories and lifetime risks in different exposure categories were investigated. Lung-fiber content was measured in a subset of cases. Australia had 7,027 cases from 1945 to 2001, with 488 more in January 2002 through June 2003. Incidence rates for Australia per million population > or = 20 years old (1999) were: male 53.3; female 10.2; total 31.8. Rates have continually increased and are the highest reported national rates in the world. Western Australia had the highest rate (1999 total 47.7), but most cases arose from the two most populous eastern states, New South Wales and Victoria. In 88% of cases (male 90%, female 61%), histories of asbestos exposures were obtained. In 80% of cases with no history of exposure, TEM lung asbestos fiber counts > 200,000 fibers > 2 microm length/g dry lung were obtained, suggesting unrecognized exposure. Australia's high incidence of mesothelioma is related to high past asbestos use, of all fiber types, in a wide variety of settings. The number of cases is expected to be about 18,000 by 2020, with about 11,000 yet to appear.