Three studies provide data on this topic. The largest was at the Ferodo factory in the U.K. There was no evidence of an overall excess in mortality from all causes, and in particular no increase in mortality due to lung cancer. Also, there was no evidence of any dose-response effect for lung cancer. There were 13 mesotheliomas but for 10 of these there had been exposure to crocidolite whilst working on a special contract that only a small minority of the workforce were involved in. Another one had worked in an asbestos-cement factory for 20 years. This left two mesotheliomas, one unconfirmed, for which the only known exposure was to chrysotile asbestos. The second study was of a plant in Connecticut. There was a significant increase in mortality due to respiratory cancer, but this excess was greatest in those with less than 1 year's exposure and was unrelated to cumulative exposure. No mesotheliomas occurred. The third study was of two factories in Ontario manufacturing automotive components. There was a non-significant increase in lung cancer mortality but the majority of these had not worked in the departments where asbestos was used. There were two unconfirmed mesotheliomas, one of whom had worked with friction materials. In conclusion, the three studies show that, if there are any effects on mortality due to working in the manufacture of friction materials, these effects must be small.