For the most patients with pulmonary tuberculosis, treatment are successful and the chemotherapy can be finished within a year. Few patients, though receiving standard anti-tuberculous chemotherapy, expectorate tubercle bacilli continuously for more than a year. They are named "chronic excretors of mycobacterium tuberculosis bacilli" or "intractable tuberculosis patients". Being suspected that this phenomenon is produced by many factors, it is necessary to correspond suitably to these patients for eradication of tuberculosis. This symposium was organized to search for some factors on the bacterium and on the host, which caused patients to be the chronic excretors or intractable patients. We hope that our discussion may contribute to take the appropriate measures for such hard diseases. The main results are summarized as follows. 1) Dr. TSUCHIYA conducted a epidemiologic study by questionaire method to 33 Japanese national sanatoriums. The total number of tuberculosis patients admitted to these hospitals on a optimal day from September to October 1994 were 1,295. Numbers of patients who had expectorated bacilli continuously for more than 12 months were 85 (6.6%). The male/female ratio was about 3, their average age was 64. They had a tendency of thin-physique and most of them had past histories of tuberculosis, being the refractory cases. The average clinico-epidemiologic conditions of the patients came before our eyes. 2) Dr. OGATA analysed the results of drug sensitivity tests of mycobacterium tuberculosis bacilli from 2,630 pulmonary tuberculosis patients which contained 179 chronic excretors. The only 2.2% of bacilli from the chronic excretors were sensitive to RFP (50 gamma). The 99.4% of bacilli showed to be resistant to INH (0.1 gamma). The 39.1% of bacilli were sensitive to streptomycin (20 gamma). To EB (2.5 gamma) 34.1% of bacilli were sensitive. However, the ratio of chronic excretors in tuberculosis patients was not increased in these 17 years, and for many cases of these chronic excretors, they are all inexperienced in PZA, multi-sensitive-drug chemotherapy including PZA and OFLX were useful. Some of them underwent lobectomy combined for effective chemotherapy. The chronic excretors are likely to be affected multidrug-resistant bacilli, and it is important for such cases to treat intensively with several kinds of sensitive drugs. 3) Dr. FUJIWARA studied Interleukin-10 (IL-10) producing function of monocytes stimulated by Mycobacterium tuberculosis (M-TB). The IL-10 usually down-regulates a number of different macrophage functions, including microbicidal activity against intracellular bacteria such as Mycobacterium species. They found that the mean IL-10 production by peripheral blood mononuclear cells (PBMC) obtained from a healthy tuberculin-reactor stimulated with multidrug-resistant M-TB was greater than that with drug-sensitive M-TB. The IL-10 producing cells were monocytes, not T-lymphocytes. They moreover found that PBMC from intractable tuberculosis patients secreted greater amounts of IL-10 than those of healthy subjects. These data may give a hint for development of new immunotherapeutic methods for multi-drug-resistant tuberculosis patients. 4) Dr. HARA analysed clinical courses of 580 consecutive cases of bacilli positive pulmonary tuberculosis admitted in his hospital from a point of underlying diseases. All of dead 24 cases had some underlying diseases; diabetes mellitus 3, chronic liver diseases 4, others 17 (malignant neoplasms, central nerve vascular diseases, malnutritional condition, etc). (ABSTRACT TRUNCATED)