The latency period for malignant mesothelioma is the amount of time between exposure to asbestos and the time when the disease becomes apparent clinically. Of the asbestos-related diseases, mesothelioma has the longest latency. On average, 35 to 40 years will elapse between exposure to asbestos and diagnosis of mesothelioma . This is only an average, and there have been cases of diagnosis 50 or more years after exposure, or in as little as 10 years. Malignant pleural (lung) mesothelioma most often is diagnosed between ages 40 and 69. A large proportion of mesothelioma patients diagnosed earlier than age 40 have a history of asbestos exposure during childhood.

While most mesothelioma patients are in their 40s to 60s, the disease can occur even in childhood, though it is extremely rare—only two to five percent of cases of malignant mesothelioma develop in the first two decades of life . Asbestos exposure in these cases may be environmental or may not be demonstrable at all, so these statistics may not apply to the current understanding of latency periods.

Higher exposure to asbestos may result in a shorter latency period. Patients showing a higher lung burden of asbestos—that is, a greater amount of asbestos fibers in the lungs on biopsy—may have shorter latency times.  The highest asbestos burden and the shortest latency times have been shown in patients who were occupationally exposed during jobs within the asbestos and insulation industries and in shipyards.

Mesothelioma comes in different forms. One primary distinction made is based on the initial site of the disease. Peritoneal mesothelioma, appearing in the abdomen, has a shorter latency period on the average than pleural mesothelioma, which appears in the chest. One study showed the mean latency period for peritoneal mesothelioma to be 28 years. For pleural mesothelioma, the mean latency period was 35 years. In this study, the median duration of asbestos exposure for pleural mesothelioma was 5 years and for peritoneal mesothelioma 11 years, but the exposure times could vary widely, ranging from a few days to over 40 years.