^99mTc-ethambutol radiopharmaceutical is a diagnostic kit based on the anti-tuberculosis drug, ethambutol, labeled with radioactive tracer ^99mTc.  This radiopharmaceutical is a result of research development in Centre for Radioisotope and Radiopharmaceutical Technology, BATAN. ^99mTc-ethambutol radiopharmaceutical in the hospital used as a diagnostic agent for tuberculosis detected, particularly tuberculosis in extra pulmonary organs that is not easily detected by existing  conventional methods. The aim of study to find out how stable ethambutol kit when stored at certain temperature and how stable ethambutol stability after labelled  with ^99mTc.  These stability data are required by hospitals which used ^99mTc-ethambutol . The stability test performed by measuring the radiochemical purity of  ethambutol kits which were stored at certain time period and labelled with ^99mTc using thin layer chromatography (TLC) method. Radiochemical purity tests were also performed on ^99mTc-ethambutol at certain time period after its labeling process.  Based on experiment results, it was obtained that ethambutol kit was still stable for up to 9 months when stored at refrigerator temperature 8 ^oC with percentage of radiochemical purity average > 85% and up to 11 months when stored in deep freezer temperature -80 ^oC with percentage of radiochemical purity average 90%. While ^99mTc-ethambutol was still stable for up to 4 hours after labeling with  percentage of radiochemical purity more than > 85%.