The synthesis of new 7-(halophenylamino)-1 cyclopropyl-6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid derivatives is described. Substitution of quinolonic compound 1a with chloro and fluoro aniline derivatives at position 7 produced target compounds 2–9 with relatively low yields. Alternatively, the product of correspondent carboxylate ester 1b subsequent with acid hydrolysis produced satisfactory yield. The prepared targets have shown interesting antibacterial properties against standard and resistant gram-positive strains. In particular, 2-chloro and 3-chloro aniline derivatives (3 and 4) depict MIC values of 6.7 and 0.9 lg/ml, respectively against standard S. aureous. Both compounds showed good activity against resistant strains of S. aureous.