The efficacy and safety of a 5-day regimen of 800 mg telithromycin once daily was compared with a standard 10-day regimen of 500 mg cefuroxime axetil twice daily in a multicentre, randomized, double-blind, parallel-group trial involving 376 patients with acute exacerbations of chronic bronchitis (AECB). In clinically evaluable patients (n = 282), post-therapy clinical cure rates were 86.4% with telithromycin and 83.1% with cefuroxime axetil. In bacteriologically evaluable patients (n = 53), eradication or presumed eradication of the pathogen was achieved in 76.0% and 78.6% of telithromycin and cefuroxime axetil patients, respectively. Adverse events were mostly mild; the most common were diarrhoea (12.8% versus 11.8%) and nausea (8.9% versus 3.2%) in telithromycin and cefuroxime axetil patients, respectively. The 5-day regimen of 800 mg telithromycin once daily was similar in efficacy and equally well tolerated as a 10-day regimen of 500 mg cefuroxime axetil twice daily in adults with AECB.