Due to the emergence of drug resistant M.leprae , there is a need to look for new drugs for the treatment of leprosy. We evaluated the effectiveness of new quinolones in vitro as well as in vivo. The in vitro and in vivo results suggested that a cyclopropyl group at the 1-position, COOH at the 3-position, OH at the 4-position, NH₂ or OH-substitutions at the 5-position, F at the 6-position, 5- and 6-membered rings at the 7-position, halogen (F or Cl) or OCH₃ at the 8-position of the quinolone core structure, remarkably enhance ant-M.leprae activities of the drug.