Young children living in close contact with a case of smear-positive pulmonary TB (PTB) are at particular risk of Mycobacterium tuberculosis infection and TB disease. Screening of the household contacts of an infectious source case is therefore recommended to identify children with TB and enable their prompt treatment, and to provide children who do not have TB with isoniazid preventive treatment. Isoniazid preventive treatment (IPT) is particularly beneficial in the case of children who are infected with the human immunodeficiency virus (HIV). A breastfeeding infant has a particularly high risk of infection from a mother with smear-positive pulmonary TB, and a high risk of developing TB. The infant should receive 6 months of IPT, followed by BCG vaccination. Breastfeeding can be safely continued in children during this period. The organisation of a system for comprehensive child contact screening depends on collaboration between the National TB Programme (NTP) and all child health providers. Close contacts of multidrug-resistant (MDR) TB patients should receive careful clinical followup for at least 2 years. If active disease develops, prompt initiation of treatment with a regimen designed to treat MDR-TB is recommended. On the basis of the currently available evidence, the World Health Organization does not recommend second-line drugs for chemoprophylaxis in MDR-TB contacts.