The aim of the study was to evaluate, in clinical conditions, the penetration of ciprofloxacin into bronchial secretions. Eight patients were included in the study. They presented with nosocomial pneumonia and were under controlled mechanical ventilation. Ciprofloxacin was given at a dose of 3 mg/kg over 30 min. Serial bronchial and blood samples were obtained over a 12 hour period on day 2 and 4. Ciprofloxacin was measured by HPLC. Serum peak levels were 2.95 +/- 1 mg/l on day 2, and 2.43 +/- 0.7 mg/l on day 4. Bronchial peak and through levels were 0.95 +/- 0.51 mg/l and 0.21 +/- 0.12 mg/l, respectively, on day 2, and 0.76 +/- 0.17 mg/l and 0.18 +/- 0.14 mg/l, respectively, on day 4. The ratio of bronchial/serum peak was 0.32 +/- 0.11 and 0.33 +/- 0.06 on day 2 and 4, respectively. The ratio of AUC 0-12 h in the bronchial secretions/AUC 0-12 h in the serum samples was 0.66 +/- 0.04 and 0.55 +/- 0.27 on day 2 and 4, respectively.