A series of new isoniazid hydrazones was synthesized by two procedures. Most of them exhibited the same activity against Mycobacterium tuberculosis (MIC 1 mmol/L) as isoniazid (INH), better activity against Mycobacterium kansasii 325/80 (MIC 0.125-0.250 mmol/L), high value of selectivity index (SI) and IC50 between 0.0218 and 0.326 mmol/L.