Moxilloxacin is a new fluoroquinolone antibacterial agent with a broad spectrum of activity, encompassing gram-negative and gram-positive bacteria. It has improved activity against gram-positive species (including staphylococci, streptococci, enterococci) and anaerobes compared with ciprofloxacin. This is offset by slightly lower activity against pseudomonal species and Enterobacteriaceae. In common with other fluoroquinolones, moxifloxacin attains good penetration into respiratory tissues and fluids and its bioavailability is substantially reduced by coadministration with an antacid or iron preparation. However, moxifloxacin does not interact with theophylline or warfarin. In clinical trials in patients with community-acquired pneumococcal pneumonia (CAP), acute exacerbations of chronic bronchitis (AECB) or acute sinusitis, moxifloxacin 400 mg once daily achieved bacteriological and/or clinical success rates of approximately 90% or higher. Moxifloxacin was as effective as amoxicillin 1 g 3 times daily and clarithromycin 500 mg twice daily in CAP and as effective as clarithromycin in AECB. In patients with sinusitis, a 7-day course of moxifloxacin 400mg once daily was as effective as a 10-day course of cefuroxime axetil 250mg twice daily. In contrast to some other fluoroquinolones, moxifloxacin appears to have a low propensity for causing phototoxic and CNS excitatory effects. The most common adverse events are gastrointestinal disturbances.