Abstract: The compounds of quinolone class, which were studied extensively and developed very quickly in the last decades, showed high activity,low toxicity and broad antibacterial spectrum. About thirty new compounds of 1,7-disubstituted-6-fluoro-1, 4-dihydro-4-oxoquinoline-3-carboxylic acids were synthesised and evaluated in vitro against S. aureus 25923, E. coli-25922 and P. aeruginosa. Their activities were low. The minimum inhibitory concentrations (MICμg/ml)of these Compounds against Gram-positive bacteria were higher than those against Gram-negative bacteria The relative in vitro activity contributed by 1-benzyl was: benzyl>p-chlorobenzyl>p-nitrobenzyl groups.