Background: Tuberculosis is a disease of global importance. Indeed, the lack of sensitive methods for the diagnosis and inappropriate therapy may lead to increased multidrug-resistance (MDR) cases. However, early detection and identification of acid fast bacilli (AFB) in clinical specimens can lead to effective intervention. Materials and Methods: The sputum specimens from 156 clinically suspected tuberculosis patients and 40 non- tuberculosis patients were digested, examined microscopically for acid- fast bacilli, and inoculated into “Mycobacterium Growth Indicator Tube” (MGIT), BACTEC –12B vial and onto Lowenstein- Jensen slants by standard procedures. Results: The result showed that smear was positive in 82(52.5%) and negative in 74 (47.5%) of 156 clinically suspected tuberculosis patients. The culture positive rate with Lowenstein- Jensen, MGIT, and BACTEC-12B vial were 122(78%), 136(87%), and 143(91%), respectively. Thereafter, MGIT indirect and direct susceptibility tests were performed on 15 sputum-positive specimens and the results were compared with proportional method. The results have revealed that accordance with proportional method was higher in MGIT indirect (83.5%) than direct (75%) susceptibility test, the difference was significant (p < 0.05). In another set of experiments, the indirect MGIT drug susceptibility test in 25 mycobacterium tuberculosis isolates were performed and compared with proportional method. The results showed that MGIT could correctly detect susceptibility to streptomycin, ethambutol, rifampin and isoniazid for 77.8%, 33%, 77.2% and 80%, respectively. Also, the agreement with proportional method for resistance were 88% for streptomycin, 80% for ethambutol, 80% for rifampin and 89% for isoniazid. Furthermore, by combining MGIT technology with L.J media, the mean time required for culture to grow for identification test was reduced from 22-28 to 12-16 days (p <0.05). Conclusion: MGIT is an efficient system to be used in center/ referral mycobacteriology laboratories of developing countries along with routine solid or liquid culture media. (Tanaffos 2002; 1(3): 35-44)