Early detection of tuberculosis (TB) is essential to improve health outcomes for people with TB, and to reduce TB transmission more effectively. Systematic screening in high risk groups is a complement to efforts to improve the patient-initiated pathway to TB diagnosis (that is, diagnosing TB among people who actively seek care with TB symptoms). In 2013, WHO published principles and recommendations on systematic screening for active tuberculosis., based on a thorough review of available evidence. Evidence suggest that screening, if done in the right way and targeting the right people, may reduce suffering and deaths. However, potential benefits need to balanced against the risks and costs of screening. Mass screening and screening in low-risk groups should be avoided since it risks wasting resources and causing more harm than good. The prioritization of high-risk groups for screening, as well as the choice of screening approach depend on the local TB epidemiology, the health-system context, and the resources available. In order to further help countries develop rational strategies for systematic screening, WHO has developed an operational guide, which provides practical guidance on how to develop a national or local screening strategy by: assessing the situation; defining the objectives of screening; prioritizing risk groups for screening; choosing screening tools, algorithms and approaches; planning and budgeting for, and implementing the strategy; monitoring and evaluating the strategy.