Between the Irkutsk Dispensary and the Irkutsk AIDS Center, it is estimated that more than 700 subjects would be eligible. The majority enrolled from the Irkutsk Dispensary will have M. tuberculosis positive specimens (anticipated ~175 total enrolled) and complete pharmacokinetic analysis. It is expected that fewer subjects (anticipated ~25) of those enrolled from the referral Irkutsk AIDS Center will commence TB treatment at Irkutsk Dispensary and complete pharmacokinetic analysis. Sample size is restricted by the exploratory/observational focus of the R21 funding source, and thus estimated upon subjects recruited/enrolled over a 12 month period.