A clinical trial was performed to evaluate efficacy and tolerability of Bay-o-9867 in the treatment of UTI and LRTI. 40 patients were admitted to the study: 27 affected with LRTI, mainly exacerbations of COPD, and 15 affected with UTI. Two patients were affected concomitantly with a UTI and LRTI. The patients were treated with Bay-o-9867 (ciprofloxacin) administered orally at a daily dosage of 500 mg (250 q 12 h) in 30 patients and of 1000 mg (500 q 12 h) in 10 patients, depending on the severity of infection. Clinical results were extremely favourable as complete clinical resolution of infective episode was achieved in 38 patients (15/15 in UTI patients; 25/27 in LRTI patients), whereas improvement was achieved in 2 (in LRTI). Overall clinical efficacy was therefore successful in 100% of cases. Concerning bacteriological results, 38 pathogens were isolated from infective sites before starting treatment, and all were eradicated (eradication rate: 100%). Tolerability was assessed as good: no adverse event was observed.