ABSTRACTObjective:To compare the clinical and antimicrobial efficacy of besifloxacin ophthalmic suspension 0.6 with that of vehicle in the treatment of bacterial conjunctivitis.Research design and methods:This was a randomized, multicenter, double-masked, vehicle-controlled study. A total of 957 patients aged 1 year and older with bacterial conjunctivitis were randomized to treatment with besifloxacin ophthalmic suspension 0.6 or vehicle applied topically three times daily for 5 days.Main outcome measures:Primary endpoints were clinical resolution and microbial eradication of baseline bacterial infection at Visit 2 (Day 5 ± 1). Secondary endpoints included clinical resolution and microbial eradication at Visit 3 (Day 8 or 9), individual clinical outcomes at follow-up visits, and safety.Clinical trial registration: NCT number, NCT00347932.Results:Three hundred and ninety patients had culture-confirmed bacterial conjunctivitis. Clinical resolution and microbial eradication were significantly greater with besifloxacin ophthalmic suspension than with vehicle at Visit 2 (45.2 vs. 33.0, p 0.0084; and 91.5 vs. 59.7, p < 0.0001, respectively) and Visit 3 (84.4 vs. 69.1, p 0.0011; and 88.4 vs. 71.7, p < 0.0001, respectively). Results for secondary endpoints of individual clinical outcomes were consistent with primary endpoints. Fewer eyes receiving besifloxacin ophthalmic suspension experienced adverse events than those receiving vehicle (9.2 vs. 13.9; p 0.0047).Conclusions:Besifloxacin ophthalmic suspension produces clinical resolution and microbial eradication rates significantly better than vehicle and is safe for the treatment of bacterial conjunctivitis.Limitations:A limitation of this study is the lack of a non-treatment control group. [ABSTRACT FROM AUTHOR]