Tuberculosis (tb) mortality, morbidity and infection prevalence were very high in Belgium and in the other industrialised countries during the previous century, and the first half of this century. Therefore tb was an "export" pathology, especially towards developing countries. At the end of this century tb-epidemiological indices reached very low levels in the Western world, while tb became endemic in several non-Western countries and so it actually has become an "import" pathology. In the USA, as well as in many European countries, the tb-morbidity incidence started to increase again about ten years ago. The risk groups are, however, not identical in the USA and in Belgium. In the USA, it is particularly the AIDS-epidemic that is the cause of half of the increase in tb-incidence; in addition social outcasts, homeless and IV-drug addicts are important risk groups and due to their poor therapy compliance they are responsible for the many multidrug resistant forms emerging in New York and other large cities. In Belgium elderly males are an important risk group with a tb-incidence of 50 per 10(5) in 1993 (versus an overall incidence of 15 per 10(5)). Besides, in this group the diagnosis is often made late. A second important risk group consists of allochthones, with an incidence of 54 per 10(5), especially non-Western allochthones, with an incidence of 120 per 10(5). Above all others are the asylum seekers with an estimated incidence of 400 per 10(5) (which undoubtedly is an underestimation). In Belgium, the AIDS-epidemic does not represent a major problem so far; only 3.5% of the tb-cases have AIDS or are HIV-positive, and 50% of these are immigrants. Finally, also multidrug resistance is no real problem, since resistance against isoniazide and rifampicin has been found in only 0.5% of the tb-cases. Contact persons of tb-cases, however, still remain a very important risk group with an incidence of more than 200 per 10(5). The danger is especially great for as long as the diagnosis has not been made in the source of infection and no therapeutic measures have been taken. While the overall tb-threat increased in the last decade, the tb-organisations (in Flanders the VRGT, Vereniging voor Respiratoire Gezondheidszorg en Tuberculosebestrijding) have been more or less dismantled, which in consequence may lead to problems in the future!(ABSTRACT TRUNCATED AT 400 WORDS)