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[en] Currently there is not a single radionuclide method to detect and locate tubercular lesions with high sensitivity and specificity. Conventional modalities (Microbiological, Radiological, Immunological and Molecular Biological) have their proven utility but they suffer from one or other drawbacks. The present work is based on radionuclide imaging technique using Tc-99m INH (Isoniazid) complex to detect and locate tuberculosis (TB) at an early stage at any anatomical site. Isoniazid (INH) was chosen as ligand because it is a specific anti-tubercular drug and has shown selective uptake in live Mycobacteria sensitive to INH. After complexation of INH with Tc-99m using an indirect labeling approach (Patent pending), labeling efficiency, in-vitro and in-vivo stability, blood kinetics and organ distribution studies were carried out in balb/c mice and New Zealand White rabbits at different time intervals up to 24 hrs. Biological activity of INH was studied after labeling by Colony Forming Unit (CFU) assay of Mycobacterium tuberculosis, on solid media (Middlebrook 7H10 Agar, DIFCO). Thigh model of localized tubercular lesion was prepared in four rabbits by injecting 500μl of 3 x 10 8 cells/ml of Mycobacterium tuberculosis (Clinical Human Isolate) live bacteria in growing phase. The localization kinetics of the radiolabeled complex wa studied in the developed animal model by injecting 70-75MBq of Tc-99m INH intravenously in the ear of rabbit and the images were taken with a Gamma-camera (ECIL) at different time intervals after injection. Labeling efficiency of Tc-99m INH was found to be> 95%. Only 2-3.5% of the tracer leached out from the complex at 24 …