In this double-blind, double-dummy study, 324 patients with clinical evidence of community-acquired pneumonia (CAP) or an acute exacerbation of chronic bronchitis were randomly assigned to receive 10 days' treatment with either amoxycillin/clavulanate 875/125 mg twice daily or amoxycillin/clavulanate 500/125 mg three times daily. At the end of therapy, clinical success rates were 92.4% for the twice daily regimen and 94.2% for the three times daily regimen. There was no statistically significant difference between treatments (p = 0.647) and the 95% confidence interval around the treatment difference indicated that the two treatments were equivalent. Treatment equivalence was also confirmed at follow-up, four weeks after the end of treatment. Both regimens were well tolerated. In conclusion, amoxycillin/clavulanate 875/125 mg twice daily is as effective as amoxycillin/clavulanate 500/125 mg three times daily for the treatment of community-acquired lower respiratory tract infections and could improve patient compliance.