Tuberculosis (TB) is a major health problem in the Western Cape, with a rising incidence which now exceeds 900 per 100 000 population. (1) In this setting, nosocomial transmission of TB is a potential risk, particularly to HIV-infected or other immunocompromised patients. Nosocomial outbreaks of TB are usually noted initially because of increasing rates of TB among previously hospitalised patients, and subsequently confirmed by molecular typing of Mycobacterium tuberculosis isolates. However, in high-incidence areas, detection is hampered by the high background level of TB within communities, delays in development of symptoms in immunocompetent persons, and the existence of multiple TB service providers. In South Africa, nosocomial outbreaks of TB have been documented among HIV-infected patients at Sizwe Tropical Disease Hospital, (2) neonates in a kangaroo mother care unit, (3) and in a rural hospital at Tugela Ferry. (4) This latter outbreak involved the spread of extensively drug-resistant (XDR) TB (defined as resistance to isoniazid, rifampicin, any fluoroquinolone and at least 1 of 3 injectable second-line drugs) (5) among a large number of HIV-infected patients with rapidly fatal outcomes. Detection of these outbreaks was facilitated by the vulnerable status of the patients, which resulted in rapid progression to disease, drug-resistant status of infecting strains, and the relative isolation of the hospitals in terms of geography or timing of exposure. It is likely that cases of nosocomial TB remain undetected in other situations. Multidrug-resistant (MDR)-TB (defined as TB resistant to both isoniazid and rifampicin) is more difficult to treat than drug-sensitive TB, requires longer courses of more toxic drugs, and has poorer outcomes. Therefore, there is particular concern regarding the transmission of MDR-TB within health care facilities in South Africa. Rapid diagnosis and rapid institution of effective anti-TB treatment, combined with appropriate infection control measures, are key factors in the prevention of nosocomial transmission of TB.