1-Substituted-6-fluoro-7-aryl-(8-fluoro)-1,4-dihydroquinol-4-one 3-carboxylic acids having antibacterial activity are prepared by reacting the corresponding alkyl 1-substituted-6-fluoro-7-bromo-(8-fluoro)-1,4-dihydroquinol-4-one-3-carbox ylate with an arylmetallic compound and hydrolyzing the ester formed.