Fluoroquinolones have a broad spectrum of activity for complicated urinary tract infections, gastrointestinal infections, respiratory tract infections, sexually transmitted diseases, and chronic osteomyelitis. Since fluoroquinolones are excellent antibiotics for a number of clinical indications, their consumption has increased rapidly, both in human medicine and in food animals. Resistance to fluoroquinolones is chromosomal mediated, involving mutations either in the target genes including DNA gyrase (gyrA or gyrB) and topoisomerase IV (parC or parE), or in the regulatory factors controlling bacterial permeability or the efflux capacity of the bacteria. This review focuses on mechanisms of fluoroquinolone resistance, including known and proposed molecular mechanisms. This review also discuses the clinical impact of fluoroquinolone-resistant bacteria.