Mass immigration from developing countries to industrialized countries entails the risk of spreading resistant strains of mycobacteria, which is associated with serious epidemiological, social and economic consequences. In the face of continuing large-scale immigration to Greece, we surveyed the number of new bacteriologically confirmed cases of tuberculosis; single resistance to isoniazid or rifampin; and multi-drug resistance, i.e. resistance to at least isoniazid and rifampin, of M. tuberculosis strains that were isolated from the first culture of sputum of immigrants in the period 1993-2002. To allow better insight, immigrants were separated to foreigners coming from South-Eastern Asia and Africa, and Greek immigrants to the Former Soviet Union who returned to their country. Findings were compared to relative data from native Greek patients in the same period. The number of newly diagnosed tuberculosis cases in native Greeks and returning Greek immigrants is constantly decreasing, probably due to higher living standards in Greece, whereas TB incidence among foreigners coming from South-Eastern Asia and Africa is rising, which may be attributed to the introduction of more effective surveillance systems in our country. Resistance of M. tuberculosis strains to isoniazid and rifampin is increasing in all three groups, most significantly in repatriated Greeks. Multidrug resistance also shows a significant increase in all three groups, particularly in repatriated Greeks. Pneumon 2005, 18(1):74-83.