Twenty patients (15 males; five females) aged 11-70 years, with urinary tract infections were treated with one 250 mg tablet of ciprofloxacin every 12 h for 5-10 days. Clinical response to this treatment was the complete disappearance of symptoms in 85% of cases and the elimination of the micro-organism responsible for infection. In only three patients, who all had urinary calculus in addition to an infection, clinical failure of the therapy occurred and the causative micro-organism persisted. Tolerance to the therapy was excellent in this study, no adverse reactions connected with the treatment being reported.