The fluoroquinolone class of antimicrobial agents has expanded dramatically in the last 5 years and will continue to grow over the next decade. This article discusses the newer fluoroquinolones in detail, including pharmacokinetics, pharmacodynamics, safety, and drug interactions, and the spectrum of in vitro activity. Newer agents are compared and contrasted with the older ones, particularly ciprofloxacin and ofloxacin, and problems with liver toxicity and trovafloxacin are described. Finally, appropriate use of the fluoroquinolones is discussed, including their role in the treatment of urinary tract infections, sexually transmitted diseases, gastrointestinal infections, osteomyelitis, and respiratory tract infections.