Moxifloxacin is a new quinolone with excellent bactericidal action against gram-positive, gram-negative, anaerobic and atypical microorganisms. There is a world tendency of shortening the time of treatment of acute sinusitis with the release of this new drug. We aim to evaluate the efficacy and the safety of moxifloxacin for seven days, in the dose of 400 mg a day, in the treatment of the acute sinusitis acquired in the community. Eighteen consecutive adult patients, with age varying from 16 to 62 years (39 year-old average), with suggestive clinic of acute bacterial sinusitis were included in the study. They received seven days of treatment (400 mg, orally, once a day). In the patients\' return we evidenced: persistence of fever in 1 (5%), indisposition in 2 (11%), pain in sinuses in 3 (17%), migraine in 4 (23%), post nasal secretion in 5 (29%), and nasal obstruction in 9 (52%). In relation to the evaluation of the efficacy by the patient, we obtained cure in 5 patient (29%), improvement in 8 (47%), and inefficacy in 4 (23%). In relation to the evaluation by the doctor, we obtained cure in 9 (52%), improvement in 4 (23%) and inefficacy in 4 (23%). The collateral effects were: nauseas in 3 patients (17%), anxiety in 2 (11%) and indisposition in 1 (5%). The results of this study suggest that the treatment of acute sinusitis with moxifloxacin (400 mg a day) for seven days is insufficient for resolution of the disease.