We studied the clinical characteristics, treatment and prognosis of multidrug-resistant pulmonary tuberculosis patients retrospectively. In this study, multidrug-resistant is defined as both resistant to 0.1 microgram/ml of INH and 50 micrograms/ml of RFP at least. From 1990 to 1997, out of 1841 culture positive pulmonary tuberculosis patients, 76 patients (4%) proved to be multidrug-resistant (53 males, 23 females, age 18-84, 40 originally treated cases and 36 relapse cases). Most of cases revealed resistance to other drugs in addition to INH and RFP. The combination of anti-tuberculous drugs were complicated and changed repeatedly. The incidences of administration of drugs were as follows; TH 62%, EB 58%, PZA 58%, KM 33%, PAS 33%, SM 29%, CS 20%, EVM 14%, CPM 3%. New quinolones, for example OFLX/LVFX, CPFX and SPFX, were also used frequently (62%). Eight percent of patients were operated. Bacteriologically effective drugs that meant culture negative were TH (14%), PZA (12%), KM (12%), EB (12%), SM (5%), new quinolones (16%). 67% of originally treated cases and 43% of relapse cases became culture negative. Many cases were treated for a long period. 19% of originally treated cases and 33% of relapse cases were treated more than three years. 11% of patients were died of tuberculosis. Major prognostic factors were diabetes mellitus (17%), malignancies (10%), non-adherence (9%) and other complications. Because of no absolutely effective treatment, we have to choose a treatment according to each patient. Development of new treatment is crucial.