This substudy of TBTC Studies 27 and 28 compares 1) the pharmacokinetics of moxifloxacin alone versus moxifloxacin administered with rifampin in healthy volunteers and 2) the pharmacokinetics of moxifloxacin among patients with tuberculosis being treated with multidrug therapy (isoniazid or ethambutol, rifampin, and pyrazinamide) to those of healthy volunteers receiving moxifloxacin plus rifampin. It also evaluates the association between polymorphisms of MDR1 genotype (P-glycoprotein) and rifampin pharmacokinetic parameters, the effect of polymorphisms of MDR1 genotype and/or rifampin pharmacokinetics on isoniazid pharmacokinetic parameters adjusted for N-acetyltransferase genotype (NAT2), and determines by multivariate regression analyses the associations between moxifloxacin or rifampin pharmacokinetic parameters and markers of tuberculosis disease severity including the covariates of two-month culture positivity, cavitary lung disease, Body Mass Index, weight, duration of study treatment prior to PK, co-morbidities and C-reactive protein. Healthy volunteers and TB patients receive frequent scheduled blood draws during a 24 hour period after ingesting a dose of TB drugs.