Quinolones are a very important family of antibacterial agents that are widely prescribed for the treatment of infections in humans. Quinolones comprise a relatively large, growing and most interesting group of antibacterial drugs which have made a major impact on the field of antimicrobial chemotherapy. Since their discovery in the early 1960s, the quinolone group of antibacterials has generated considerable clinical and scientific interest. The bacterial type II topoisomerases, DNA gyrase and topoisomerase IV are validated targets for clinically useful quinolone antimicrobial drugs. A significant limitation to widely utilized quinolone inhibitors is the emergence of drug-resistant bacteria due to an altered DNA gyrase. Antibiotic drug choice will remain difficult in the presence of increasing resistance, but introduction of the new quinolones has created a new and exciting era in antimicrobial chemotherapy.