Aminoglycosides like amikacin are frequently administered in the treatment of suspected or proven Gram-negative infections in neonates, often in combination with penicillins. Due to a concentration-dependent killing combined with a postantibiotic effect, the bactericidal efficacy of amikacin relates to its peak serum concentration. Consequently, therapeutic peak levels at the infection site will define the effectiveness of antibiotic therapy. Renal side effects and ototoxicity relate to the trough serum amikacin concentration, based on the saturation of renal and cochlear cell-binding sites. The pharmacokinetics (PK) of amikacin displays extensive interindividual variability, which makes it difficult to achieve an effective and safe administration in the individual neonate (1).Based on maturational differences in body composition and renal immaturity in early life, differences in both distribution volume (V d , in liters/kg) and clearance (CL t , in ml/kg/min) of this hydrophilic drug have been observed. Because of the higher water content in preterm infants, and thus a higher distribution volume for hydrophilic drugs, a relatively higher amikacin dose is necessary in this population (3,25).Since pulmonary infections can be a major cause of neonatal morbidity and mortality, antibiotic levels in bronchial secretions and bronchial and alveolar epithelial lining fluid (ELF) are of specific interest. Measuring antibiotic concentrations in the lung is not easy and is usually represented by ELF concentrations. Keeping the anatomy of the blood-bronchial barrier in mind, one can imagine that to reach ELF, the antibiotic must pass through the epithelial lining cells linked by tight junctions (14). Consequently, biochemical characteristics like the degree of protein binding and the lipophilicity and diffusibility of the antibiotic will influence antibiotic concentrations in interstitial fluid and in ELF. In adults, we are aware of studies to assess the blood-alveolar barrier after parenteral administration of amikacin. Dull et al. showed that, after intramuscular (i.m.) administration, the highest amikacin serum concentration correlated significantly with the highest bronchial secretion concentration of that individual and that elimination of amikacin from serum and bronchial secretions occurred at approximately the same rate, with a peak concentration that is blunted in the alveolar compared to the blood compartment (12). Since data in neonates are lacking, the aim of this study is to describe amikacin concentration in the bronchial ELF of newborns.