Mesothelioma has been such a rare disease, or one recognized so infrequently, that it has not been coded as a separate cause of death and has been seriously underestimated in mortality statistics.^{7, 8} The age-adjusted incidence of pleural and peritoneal mesothelioma in the United States is estimated at 14.2 per million per year, with almost a threefold increase for pleural mesothelioma in white males between 1973 and 1984.⁸ The male:female ratio is approximately 4:1, and 80% arise from the pleura.⁸ Cases tend to be clustered in areas of asbestos product plants and shipbuilding facilities.⁹ Similar trends have been reported in other industrialized countries, such as England.¹⁰ In autopsy studies, the frequency of malignant mesothelioma varies from 0.02% to 0.7%, with a rate of 0.2% in the largest series.¹¹

In most hospital series, the pleura is more often involved than the peritoneum, with a predominance of the right side over the left (60:40).¹¹ In some epidemiologic studies monitoring cohorts of asbestos workers, however, the peritoneal form is more common than the pleural.¹

The mean age of patients is approximately 60 years,^{12, 13, 14, 15} but the disease can occur at any age, including in childhood.¹⁶ In a review of 80 children with a diagnosis of malignant mesothelioma, the mean age was 9.7 years, and 59% were male. Only 2 children were noted to have a history of possible asbestos exposure—1 had received radiotherapy for Wilms tumor and 1 had been exposed to isoniazid in utero.¹⁷