OBJECTIVES: The aim of this study was to evaluate the comparative effectiveness and safety of short (5 days) and long (7 or 10 days) duration antimicrobial treatment of patients with acute exacerbations of chronic bronchitis (AECB). METHODS: We performed a meta-analysis of randomized controlled trials (RCTs) comparing regimens of the same antibiotic (same dosage and same route of administration) administered for a different time period. We searched PubMed, the Cochrane Central Register of Controlled Trials and reference lists from publications, with no language restrictions. RESULTS: Of the 1031 reports retrieved initially, seven RCTs, enrolling 3083 patients with AECB, met our inclusion criteria. The antimicrobials studied in these seven RCTs were quinolones, cefixime and clarithromycin. There was no difference between the short- and long-duration therapies with regard to treatment success in intention-to-treat [relative risk (RR) = 0.99, 95% confidence interval (CI) 0.95-1.03], clinically evaluable (RR = 0.99, 95% CI 0.96-1.02) or microbiologically evaluable (RR = 0.98, 95% CI 0.93-1.02) patients. Short-duration treatment, when compared with long, was associated with fewer adverse events (RR = 0.84, 95% CI 0.72-0.97). CONCLUSIONS: Short-duration treatment seems to be as effective as and safer than long-duration antimicrobial treatment of patients with AECB. Additional research is required to clarify the long-term outcomes (namely the exacerbation-free interval after the resolution of an initial episode) of the compared regimens.