Introduction: Gatifloxacin is a new broad-spectrum fluoroquinolone with excellent activity against prevalent respiratory bacteria, including penicillin-resistant Streptococcus pneumoniae and other atypical pathogens. Aim: The aim of this study was to evaluate the efficacy and safety of gatifloxacin in patients with acute bacterial sinusites. Material and method: In this multicenter, open label, prospective study, 2787 adult outpatients with the diagnosis of acute bacterial sinusites, were treated with gatifloxacin 400mg PO once a day, for 10 days. A standard report form was filled by an unpaid voluntary physician, who evaluated the patient, based on adverse events and efficacy criteria. Results: The global rate of cure and improvement was 96,2%. The incidence of relapse (0,6%) and therapeutic failure (1,1%) were low. Conclusions: Oral gatifloxacin, 400mg once a day, is effective and safe for patients with acute bacterial sinusites.