Acute exacerbations of chronic bronchitis (AECB) and chronic obstructive pulmonary disease (COPD) are associated with significant healthcare costs and contribute to the progress of the disease. Although a number of factors may trigger these episodes, between 40% and 60% are bacterial in nature. Antimicrobial therapy can be effective in treating exacerbations, leading to improved peak expiratory flow rates, fewer hospitalizations, lower relapse rates, and greater clinical success. Evidence suggests that short-course antimicrobial therapy can be as effective as standard duration therapy (>7 days) in treating exacerbations. Randomized trials have shown that clinical and bacteriological success rates are comparable with both 5-day and standard antibiotic courses. Furthermore, 5-day fluoroquinolone therapy is associated with faster recovery, fewer relapses, prolonged duration between episodes, and less hospitalization when compared with standard therapy. Both moxifloxacin and gemifloxacin have received FDA-approval for 5-day therapy in AECB.