The fluoroquinolones represent an important advance in antimicrobial therapy. Commercially available products in the United States now include norfloxacin, ciprofloxacin, ofloxacin, enoxacin, and lomefloxacin. Although they share a common mechanism of action, they differ significantly in their antimicrobial spectrum of activity, their pharmacokinetic characteristics, and, to a lesser degree, their safety profiles. These compounds are generally highly effective against aerobic gram‐negative and many gram‐positive isolates; their activity is more limited against anaerobic bacteria. Quinolone‐resistant bacteria have been isolated, but most do not appear to pose a clinically significant problem at this time. The agents are effective in the treatment of a wide range of infections. Although some, such as ciprofloxacin and enoxacin, have been associated with clinically significant interactions with theophylline derivatives, others such as ofloxacin and lomefloxacin appear to have a limited propensity for such interac