In view of their antimicrobial activity and pharmacological properties, fluoroquinolones should be suitable for the treatment of lower respiratory tract infections. The overall clinical success rate using enoxacin, ofloxacin, pefloxacin, and ciprofloxacin ranges from 81 % to 89 %. Despite relatively high MICs of the fluoroquinolones forStreptococcus pneumoniae, the clinical success rate of these drugs in pneumococcal infections is 91 %, but the eradication rate of this pathogen is lower (73 %). In addition, fluoroquinolones appeared to be as effective as standard antibiotic regimens for treatment of bronchopulmonary infections in most of the comparative trials reported. The new quinolones could be a good alternative for treatment of acute exacerbations of chronic bronchitis, especially if examination of the sputum reveals gram-negative pathogens. In community-acquired pneumonia, drugs other than quinolones seem indicated because of the limited efficacy of the new quinolones in the treatment of severe pneumococcal infections and the poor activity of these drugs against the anaerobic flora causing aspiration pneumonia. In contrast, new quinolones should be very suitable for treatment of nosocomial pulmonary infections due to gram-negative pathogens. Quinolones used with or without erythromycin and rifampin, might be useful in the treatment of Legionnaires' disease. The role of these drugs in treatment ofChlamydia andRickettsiae infections remains to be defined.