Over a period of 18 months 76 patients presenting with acute exacerbations of chronic otitis were enrolled in this study. The mean age of the patients was 46.4 ± 16.8 years, the interval between the onset of symptoms of otitis and enrolment in the study was 22.1 ± 19.4 years and the infective episode had been developing for 36.4 ± 72.4 days. The patients received either 500 or 750 mg ciprofloxacin twice daily for a period of 9 days with no topical antibiotic treatment. The bacteriological specimen taken at enrolment was positive in 93% of the patients and led to the isolation of 85 microorganisms, 65% of which were Pseudomonas aeruginosa, Staphylococcus aureus or Proteus mirabilis. At the end of the treatment period, discharge from the ears (the primary clinical evaluation criterion) had ceased in 44/69 (64%) patients examined. The clinical cure rate was 23/39 (59%) for patients treated with 500 mg ciprofloxacin twice daily and 21/30 (70%) for those treated with 750 mg twice daily (difference was not statistically significant). At the end of a 4-week post-treatment follow-up, the clinical relapse rate was 7%. There was no relapse in the patients with chronic otitis which had been bacteriologically documented. Eight adverse effects were observed in five patients and treatment had to be discontinued in one case. This study shows ciprofloxacin to be an effective and safe agent for use in the treatment of acute exacerbations of chronic otitis treated in general practice. In certain cases, however, additional treatment with a topical antibiotic may be desirab