A prospective study was performed to test efficacy of a single dose of 750 mg oral ciprofloxacine in comparison with 600 mg rifampicin twice daily for 2 days in eradicating Neisseria meningitidis from healthy nasopharyngeal carriers. Nasopharyngeal samples were obtained for culture before and 1 and 2 weeks after therapy. We found 54 (18%) of 300 healthy adult volunteers to be carriers of N. meningitidis. Of these, 51 were considered suitable condidates for evaluating the efficacy and safety of the drugs. One week after therapy, the eradication rates for ciprofloxacine and rifampicin were 92% and 96%, respectively; at 2 weeks, they were the same. The difference in the eradication rates of the two drugs was evaluated using the Chi-square test, and this was not statistically significant. No clinically important side-effects were associated with either drugs. A single dose of ciprofloxacine provides an effective and safe alternative to rifampicin in eradicating meningococcal carriage.