The objective of this study was to evaluate the penetration of fosfomycin in bronchial secretions in 11 tracheostomized patients which allowed sampling at successive times, following intravenous injection of 4 gr of the drug during 4 hours. In simultaneous samples of serum and bronchial secretions, the measurement of fosfomycin was performed according to the agar diffusion microbiological method. The results of the study showed a worthwhile penetration of fosfomycin, with a mean bronchial concentration reaching 13,1 micrograms/ml, half an hour after the end of the injection, decreasing slowly with 7,04 micrograms/ml remaining two hours after the injection. The ratio between bronchial levels and corresponding serum levels reached 13% two hours after the injection. Fosfomycin diffusion from serum to bronchial secretions realizes significant amounts that are superior to the MICs of fosfomycin for most bacteria responsible for serious broncho-pulmonary infections in intensive care units.