HIV-1 infection is a major cause of worldwide epidemic of tuberculosis. HIV-1 infection, even in its early stages, markedly reduces effective immune response to M. tuberculosis. In Japan, the cumulative number of the patients reported is 131 by the end of 1999 with 10 to 20 annual new cases. Most of Japanese cases are advanced AIDS patients with low CD4 number less than 100/ml. The peak of Japanese patient age is 40 to 60 years old, whereas that of foreigners is 20-30 years old, suggesting that most Japanese cases are recurrent tuberculosis. There is increasing clinical evidence that coinfection with M. tuberculosis accelerates progression of AIDS. We found that, in vivo, HIV-1 load and mutation increase in involved lung segments in patients with pulmonary tuberculosis. The promotion of HIV-1 production is not only due to activated translocation of a nuclear factor, NF-kB, but also due to reduced inhibitory factor, C/EBPb 16 kD which binds to HIV LTR and represses the transcription of HIV-1..