Mesothelioma is a malignant tumor most commonly found in the pleura, and asbestos is virtually the only established cause to date. It generally develops 30 to 40 years after the onset of exposure. Due to the increased use of asbestos since the beginning of the century in various industrial sectors, the incidence of this previously very rare disease has been rising sharply since the 1950s and 1960s in industrialized countries. The National Mesothelioma Surveillance Program (PNSM) was launched in 1998. This is a collaborative effort involving specialists from various fields. This study updates, on the one hand, the estimate of the I/M ratio (Incidence/Mortality ratio) conducted in 1992 in two regions (Île-de-France and Provence-Alpes-Côte d'Azur), and, on the other hand, the estimate of the incidence of pleural mesothelioma conducted in 1995 based on an analysis of data from the Francim network’s cancer registries collected over the 1979–1992 period. This I/M estimate was used in more recent studies which, by adjusting mortality data for pleural cancer, provided projections of the trend in mesothelioma mortality.