The efficacy and tolerability of oral cefixime 400mg once daily for 5 days was compared with standard 10-day therapy in a multicentre, double-blind, randomised, controlled clinical trial of 222 patients with acute exacerbations of chronic bronchitis. Clinical and bacteriological efficacy were assessed after 6, 11 and 30 days. A total of 167 patients were evaluable for efficacy on a per-protocol basis. Clinical efficacy (cure or improvement based on the quality and quantity of expectorated sputum and symptoms of dyspnoea) at day 11 was statistically equivalent (p < 0.01) between the treatment groups, with a successful clinical response achieved in 91% (5-day) and 89% (10-day) of patients. Bacteriological efficacy was also similar with 5- and 10-day treatment. During treatment, more patients reported an adverse event possibly or probably related to the study medication in the 10-day than in the 5-day treatment group (19 vs 14%). However, this difference was not statistically significant. Oral cefixime 400mg once daily is an effective and well tolerated treatment for acute exacerbations of chronic bronchitis. Short-term (5-day) therapy offers clinical efficacy similar to that of standard (10-day) therapy.