 This study, conducted jointly by researchers at the National Masan TB Hospital, Asan and Samsung Medical Centers in Seoul, Republic of Korea, and the Yonsei University and the NIH in the United States, will examine why some patients with tuberculosis TB develop disease that is harder to treat than most cases. TB is an infection of the lung that usually can be successfully treated with anti-TB drugs. However, some people get a more serious kind of disease called multi-drug resistant TB or extensively drug-resistant TB that is very difficult to treat and may not be cured by the regular medicines available. This study will try to find out if some of the common TB drugs are getting to the place where the TB bacteria are. It will also look at how current anti-TB drugs might be used more effectively and how better drugs might be developed. 