Rationale - Current treatment of smear positive pulmonary tuberculosis requires a minimum of 6 months, a treatment duration that is challenging for patients and tuberculosis control programs. Therefore, a high priority in tuberculosis research is the identification of agents that can shorten treatment. Several fluoroquinolone antibiotics have potent activity against Mycobacterium tuberculosis (M. tuberculosis) in preclinical testing. Of the currently available fluoroquinolones, moxifloxacin has excellent activity in vitro and in animal models of tuberculosis, a favorable pharmacokinetic profile (serum half-life of 10-12 hours), lack of problematic drug-drug interactions, no need for dosage adjustment for renal and hepatic insufficiency, and an excellent safety profile. In addition, in the murine model of tuberculosis, the substitution of moxifloxacin for isoniazid resulted in significant reductions in the time to culture conversion and the time to sterilization when compared to the standard combination rifampin, isoniazid and pyrazinamide. However, moxifloxacin has not been fully evaluated in humans for tuberculosis treatment. There is a need to assess not only the anti-tuberculosis activity of moxifloxacin-containing regimens, but also the safety of more prolonged therapy with moxifloxacin.