The efficacy and safety of long-term ciprofloxacin therapy in the management of severe bronchiectasis were retrospectively assessed in patients who had taken oral ciprofloxacin continuously for at least 90 days. The drug was well tolerated, with only one reported side effect. Treatment resulted in a symptomatic improvement in seven of the ten patients and significant improvements in peak expiratory flow rate and residual volume. There was a decrease in the number of infective exacerbations from 6.2 +/- 2.9 during 365 days to 0.5 +/- 0.53 during 412 days. Resistance to ciprofloxacin developed in 2 patients with Pseudomonas aeruginosa infection and this was associated with clinical deterioration, but in a further two patients with P. aeruginosa the pathogen was eradicated. Two patients had persistent Streptococcus pneumoniae cultured from sputum but this was not associated with clinical deterioration. The study suggests that ciprofloxacin is effective and safe in the long-term treatment of chronic bronchial sepsis due to bronchiectasis, but emergence of P. aeruginosa resistance is of some concern.