Pooled data from three randomized, double-blind, multi- centre studies evaluated the efficacy and tolerability of telithromycin 800 mg once daily for 5 days vs. standard comparators (10-day amoxicillin-clavulanate 500/125 mg three times daily, clarithromycin 500 mg or cefuroxime axetil 500 mg twice daily) in the outpatient treatment for acute exacerbations of chronic bronchitis. Per-protocol clinical cure rates at post-therapy/test of cure (days 17-24) were 86.0 and 85.8% for telithromycin and comparators, respectively, and 79.1 and 78.7%, respectively, at late post-therapy (days 31-36). Clinical cure rates were comparable for patients at increased risk, including those of > or =65 years and those with severe infection or significant airway obstruction (telithromycin, > or =77.1%; comparators, > or =75.0%). Telithromycin was well tolerated. Most adverse events considered possibly related to study medication were gastrointestinal and of mild intensity. In conclusion, 5-day telithromycin therapy is as effective and well tolerated as 10-day treatment with standard comparators.