This report reviews the literature concerning tuberculosis resulting from infection with Mycobacterium bovis in man and cattle and summarises data derived from surveillance of M. bovis in England and Wales from 1986 to 1990. Of the 228 isolates of M. bovis examined in this period, 122 (53%) were from patients aged over 60 years and are largely the result of reactivation of infection acquired prior to the institution of control measures. However, eight isolates (3.5%) were from patients aged less than 30 years. The potential sources for these presumed primary infections include the few remaining cattle infected with M. bovis or infectious human cases in the United Kingdom. However, infections acquired abroad, especially in immigrants, may account for some of these cases. Outbreaks of tuberculosis due to M. bovis continue to occur in cattle. Wild animals, particularly badgers, have been implicated as reservoirs of the infection. However, man may also prove to be an important reservoir of M. bovis for cattle as well as humans.