Ciprofloxacin, a 4-quinolone derivative with a wider spectrum of activity as compared to classic quinolones employed in the therapy of urinary tract infections, was studied in view of its possible application in the therapy of bronchopulmonary infections. An oral dose of 500 mg every 12 h was administered and both the clinical response and the pharmacokinetic profile were investigated. A complete recovery was reached in 87.5% of patients and an improvement in 12.5%; no failure was recorded. A very good penetration in sputum was confirmed by the sputum/serum area under curve ratio, providing evidence for a high bioavailability in bronchial secretion. Lung tissue concentrations confirmed the good peripheral distribution of ciprofloxacin. A twelve-hour administration schedule allows high peripheral concentrations to be obtained superior or equal to the minimum inhibitory concentrations for many pathogens.