We will invite all general practices in Hackney to take part. Practices that agree will then be randomly allocated (by a computer programme) into two groups: practices who will screen and those who will carry on as usual without screening. The project researcher responsible for data collection will not know to which group the practices have been assigned. Practices allocated to the screening group will be offered a programme designed to encourage screening as part of the new patient registration checks (by practice nurses and GPs) and during children's transfer-in visits (by health visitors). The programme is founded on proven ways of helping people change how they work and includes the following: an education programme run by the primary care research team, with a local chest consultant as opinion leader; Heaf guns, Heaf heads, and tuberculin (to test for presence of TB); TB screening guidelines; regular support and advice from the local TB specialist nurse; incorporation of a TB screening template into the practice computer consulting system; and an incentive fee paid to the practices for carrying out the Heaf tests. TB identication rates for both groups will be ascertained after 25 months of screening. The cost of implementing the screening process will also be measured.