The concentrations of cefepime in bronchial mucosa were measured after intravenous administration of a single 2 g dose in 20 patients undergoing diagnostic fibreoptic bronchoscopy. These concentrations were compared with simultaneous serum concentrations. The mean bronchial mucosal concentration was 24.1 mg/kg (s.d. 17.8 mg/kg) and the mean serum concentration was 40.4 mg/l (s.d. 28.1 mg/l). The mean percentage penetration was 59.8% (s.d. 12.5%). We conclude that a twice daily dosing of cefepime would be adequate for most respiratory infections although an 8-hourly dose may be necessary in pseudomonal infections.