The wide spectrum of antibacterial activity of cefmenoxime as well as its resistance to β-lactamase degradation, confers upon this drug a probable efficacy in the treatment of common respiratory infections. The objective of this study was to evaluate the penetration of cefmenoxime into bronchial secretions taken in patients, mostly with chronically superinfected bronchial pathology. Bronchial samples were collected by means of fiber-optic bronchoscopy; simultaneous serum samples were also taken after bolus intravenous injection of 1 g of cefmenoxime, after a single dose in 12 patients (group I); after multiple doses in 12 patients (group II). Concentrations of cefmenoxime were determined by means of microbiological procedure. The results showed: bronchial kinetics of cefmenoxime similar to those of other cephalosporins studied previously; after multiple doses a bronchial steady state with a slow decrease of bronchial levels as a function of time; no difference between levels measured after single or multiple doses; a ratio between bronchial levels (B) and simultaneous serum (S) levels (B/S, %) of about 10% at the 2nd hour, 20% at the 4th hour. Due to the extremely low MICs for most bacteria responsible for respiratory infections, cefmenoxime might be expected as the drug of choice in the treatment of bronchopulmonary infections