Fluoroquinolones are the type of antibacterial agents more extensively used from the past few years and will be continued to be used even in the next decade. The fluoroquinolones show their action by inhibiting the DNA gyrase and topoisomerase enzymes. The main mechanism fluoroquinolones is mutations that alter the accumulation of fluoroquinolones in bacteria. The broad use of the fluoroquinolones is discussed. They are useful in the treatment of urinary tract infections, prostatitis, sexually transmitted diseases, gastrointestinal infections, osteomyelitis, and respiratory tract infections. Their structure–activity relationship is also discussed and that is helpful in ongoing new researches on quinolones that may enhance the antibacterial activity of quinolones.