Between September 1996 and March 2000 for 273 smear and culture positive pulmonary tuberculosis patients (old 0/86, new0/ 187) pretreatment susceptibility tests of isolated bacilli to INH, RIF, EMB and STM were performed by standard proportional method and the results were attributed to three groups: (I) newly diagnosed without any history of treatment; (II) patients with history of treatment for one course; (III) patients with history of treatment for two or more courses supposed to be MDR cases.