Increasing resistance among the common respiratory pathogens has encouraged assessment of alternative agents, for example, levofloxacin. Unlike earlier quinolones, levofloxacin has excellent activity against Streptococcus pneumoniae, including strains resistant to penicillin. Clinical trials show levofloxacin to be as effective as cephalosporins in acute exacerbation of chronic bronchitis and as effective as co-amoxiclav, cephalosporins or amoxycillin in community-acquired pneumonia. Levofloxacin is rarely associated with serious adverse events. Nausea, diarrhea, headache and rash are the most common adverse events but are observed less frequently than with some other new quinolones.