Moxifloxacin (MXF) is the latest broad-spectrum fluoroquinolone marketed worldwide. It has in vitro activity against a wide range of Gram-positive and Gram-negative pathogens including anaerobes and intracellular organisms, as well as strains resistant to beta-lactam or macrolide antibiotics. For relevant respiratory pathogens, MXF attains the threshold values of pharmacodynamic indices predictive of clinical efficacy and minimization of resistance development. On the other hand, due to its limited activity against Pseudomonas aeruginosa, it is less suitable for 'late-onset' nosocomial infections. In clinical trials, it has been found to be at least as effective and safe as comparators, while often showing higher bacteriological success rates. In some randomized studies MXF has shown superiority over comparator regimens in the treatment of patients with community-acquired pneumonia and acute bacterial exacerbations of chronic bronchitis. A consistent observation in many clinical trials of respiratory tract infections is the early onset of effect and a faster resolution of symptoms compared with standard therapy, possibly resulting from its fast distribution into tissue and high bactericidal activity leading to more rapid bacterial eradication. Although originally developed for respiratory tract infections, MXF over the years as been shown to be effective, and consequently received approval for additional indications.