 Eligible consenting subjects will be randomized in equal numbers to 9INH or 4RIF, by a web-based registration and randomization program, stratified by site in blocks of variable size 2-8 subjects. Subjects will be followed by their usual providers during therapy and then every 3 months up to 28 months post-randomization or the occurrence of a study end-point. The primary study outcome is the occurrence, during the 28 months after randomization, of microbiologically or histologically confirmed active TB. The final diagnosis will be based on the majority opinion of an independent 3-member clinical review panel, who will review all subjects investigated for TB, without knowledge of study drug, nor the clinical diagnosis. Planned sub-group analysis will compare rates of active TB in those who complete treatment per protocol efficacy. Secondary outcomes include occurrence of confirmed plus probable active TB, Grade 3-4 adverse events judged by another blinded, independent 3-member panel as in Phase 2, occurrence of drug resistant active TB, and costs - from the health system perspective. To accomplish this, in Canada one site has been added in Vancouver, the site in Brazil is doubled, and new sites in Korea, Australia, Indonesia, Benin, Guinea and Ghana West Africa have been added. 