Moxifloxacin is a new group IV 8-methoxyquinolone. It is slightly less active than ciprofloxacin against enterobacteria and much less effective against P. aeruginosa. However, moxifloxacin is clearly better than ciprofloxacin in treating atypical microorganisms and especially anaerobic bacteria and aerobic Gram-positive cocci, including methicillin-resistant Staphylococcus aureus and penicillin-resistant Streptococcus pneumoniae. In recent years there has been an increase in the resistance of some respiratory pathogens to beta-lactam and macrolide antibiotics. Bearing in mind that moxifloxacin is well tolerated, its microbiological properties and pharmacokinetic characteristics mean that it will undoubtedly be useful in treating certain infections, particularly community-acquired respiratory infections, hospital-acquired respiratory infections caused by aerobic Gram-positive cocci, infections caused by anaerobic bacteria and skin infections. Studies have shown that moxifloxacin is effective and well tolerated in all of these conditions.