Recent progress of molecular genetics has been providing tools for new approaches to disease treatment and diagnosis of Mycobacterium tuberculosis. In 1998, Cole et al. reported the complete genome sequence of Mycobacterium tuberculosis. The new information will provide us the knowledge and understanding of the biology of Mycobacterium tuberculosis. Further, it will provide us new conception of diagnosis and treatment of the disease. Four topics were selected in this symposium. Dr. Iinuma reviewed and prospected the clinical utility of nucleic acid amplification methods of Mycobacterium tuberculosis. Dr. Suzuki reviewed the molecular mechanism of acquired resistance to anti-TB drugs and reported the early detection of genetic mutation by new designed DNA tip method. Dr. Takahashi reviewed the method of molecular epidemiology and genetic elements as a tool for strain differentiation of tuberculosis. Dr. Mizuguchi interpreted the essential feature of mycobacterial genome maps, and genes and their biological activity. He also reviewed the importance and the utility of the complete genome sequence of tuberculosis in association with pathogenecity. These topics were summarized in this report, based on the symposium of "Molecular genetic approaches to Mycobacterium tuberculosis" in the 75th annual meeting of the Japanese Society for Tuberculosis.