In vitro susceptibility of 40 Mycobacterium tuberculosis isolates to amoxycillin-clavulanate, which were isolated from various clinical specimens and 33 of which were susceptible to first line-drugs and 7 of resistant to more than one antimycobacterial agents were investigated by using E-test. It was determinated that MIC50 and MIC90 values of amoxycillin-clavulanate for susceptible strains were 8 mg/ml and 96 mg/ml, respectively. These values in multiple-drug resistant M. tuberculosis isolates were found as 48 mg/ml and 256 mg/ml, respectively. According to the results of our study, amoxycillin-clavulanate combination has effective antimycobacterial activity especially against the susceptible strains.